If you want to activate a used iPhone, you have a few options. The first option is the easiest: take it to an AT&T Wireless store (or Verizon/Sprint Store for CDMA iPhones), set up a new account, and receive a new SIM card. A second option is to jailbreak the iPhone and use it as an iPod touch without phone service. A third option is to jailbreak and unlock the iPhone for use on another carrier like T-Mobile.
Take the iPhone to AT&T Wireless
If a friend or loved one gives you their old iPhone, you can make it your own by taking it to an AT&T store and telling them you have an old iPhone and would like to use it as your own. You’ll have to sign up for AT&T service, and they’ll give you a new sim card. Once you install the SIM card, you can activate the iPhone at home using iTunes. This is by far the easiest way to activate and reuse an old iPhone.
Can I Use a Carrier Other Than AT&T or Verizon?
It is possible to unlock the original iPhone, iPhone 3G, 3GS, and GSM iPhone 4 so that they work on T-Mobile in the US, although they won’t work on T-Mobile’s 3G data network, only T-Mobile’s last-gen EDGE data network. This will mean slightly slower speeds.
The CDMA (Verizon & Sprint) iPhone 4 cannot be unlocked and can only be used on Verizon/Sprint in the US.
We don’t recommend unlocking, but if you want to do it, it is not illegal. An unlocked iPhone can be a hassle, however. For example, you won’t be able to take advantage of Apple’s iPhone software updates until the people who created the unlocking software tell you it’s ok to update.
Someone Wants to Give Me Their Old iPhone. What Do I Need to Do?
If a friend or family member wants to give you their old iPhone, and you want to use it as a phone, ask them to erase all content on the iPhone before giving it to you. This is done on the iPhone by going into Settings > General > Reset > Erase All Content and Settings > Erase iPhone. Note that this erasing process can take up to two hours.
If you want to use the iPhone just as an iPod touch without phone service, read the section immediately below.
Can I Use the iPhone Without Phone Service (Like an iPod Touch)?
Yes, and it will work with iTunes too, allowing you to buy and synch music and apps from the App Store. But, you should ask the person who’s giving you the used iPhone to keep the original SIM card inside the iPhone. Your friend will have to tell AT&T to disable their old SIM card and get a new one. The reason you should keep the old SIM card inside the iPhone is so that you can take advantage of new software upgrades and restore your iPhone.
Your friend should also restore the iPhone before giving it to you so all his data is erased. Just make sure the iPhone is activated (you can open apps, etc) when it is given to you.
What If There Is No Sim Card Inside the Used iPhone?
As long as the previous owner hasn’t left the iPhone in a restored, unactivated state, you can still use all the iPhone’s features (including synching with iTunes) except for the phone functions.
Without the original SIM card, you won’t be able to install software updates from Apple or restore the iPhone until you get a new SIM card.
If you restore or install one of Apple’s upgrades without a SIM card, the iPhone will stop working. It won’t work again until you activate it with a new SIM card or jailbreak it.
In other words, do not restore or attempt to upgrade the iPhone unless you have the original SIM card inside.
I Have an Unactivated Used iPhone Without a SIM Card. How Do I Activate It?
If you’re not going to take the iPhone to AT&T or Verizon to activate it, your only option is to jailbreak it. The term jailbreaking essentially means hacking the iPhone so that you can do whatever you want with it, including installing applications that are not approved by Apple and then unlocking it for use on other wireless phone carriers.
How Do I Jailbreak and/or Unlock My iPhone?
To jailbreak and unlock your iPhone, you’ll need to download some free software. The jailbreak software you’ll need depends on the software version of your iPhone. Your best bet to find the latest jailbreak and unlocking software is to Google the terms Jailbreak and whatever version of the iPhone software is on your phone (for example, Jailbreak and iPhone 4.2.1). Note that oftentimes, when a new iPhone software update comes out, it can take a while to figure out how to do jailbreak it, so jailbreaking/unlocking software may not be available for your version yet. Some advice: do not ever pay for jailbreaking and unlocking software, as the software is always offered for free. Another suggestion for instructions on how to jailbreak your iPhone is to check out this page on iClarified.com. They have step-by-instructions for jailbreaking every version of the iPhone and iOS software.
Just for clarification, can you use ANY iPhone sim card to enable an iPhone after it is upgrade?
For example, if I purchase a used, activated iPhone without a SIM card from someone. A year later, I upgrade the phone. Do I need the SIM card that was originally in the phone or can I use ANY iPhone sim card?
I am thinking about purchasing an iPhone (used) instead of an iPod Touch. I work with iPhone developers, so borrowing an iPhone SIM card each upgrade would not be difficult at all.
A FREIND IS GIVING ME THEIR OLD IPHONE, IT HAS TONS OF APPS ETC ON IT, BUT NO SIM CARD. WHERE DO I BUY A SIM CARD SO THAT I CAN GET UPDATES, ETC? I ONLY INTEND TO USE IT AS AN IPOD TOUCH, NOT A PHONE AT ALL.
jlorip you just go to at&t for free and ask for a sim card
i have been given an iphone without a sim card.how do i activate the phone so i can use on prepaid? i will not accept a sim card i have bought from the shop
I have a older iphone given to me 1.5 years ago by a friend. I put my ATT sim card in it and it has always worked fine- I have it on WIFi only no data plan. Can I update to 3.0 firmware? I have never unlocked it or jailbroken it etc-
I appreciate your help.
an 8 gig i phone was given to me as a hand-me-down and i would like to use it. i placed my current sim card in and tried activating the phone with itunes but i’m not sure if its trying to create another account in the process. is it possible to use the phone without having to create anything, keeping everything hassle-free or is the phone pretty much useless?
i found an iphone with no sim and so i took it completely erased it and now realized i shouldn’t have because now when i put my sim card in it says connect to itunes so i did and it said sim is not compatible so i call rogers says i need the pervious owners info ( wont happen ) and no i just wanna bye pass the main screen where it only says slide for emergency PLEASE HELP!!
Jailbreak it.
How did you get a wifi only plan?
He means he only uses the iPhone’s WiFi with his home WiFi network and other WiFI connections. There is no WiFi only plan, although if you subscribe to AT&T DSL, you can use their hotspots for free.
I have a locked iphone 3gs 3.1.3 new bootroom and baseband 5.12.01. I can’t unlock it. Can I use it with any other official carrier in Dubai (eg. Du). the phone is originally bought from US( AT&T). please help
Try Etisalat. They actually sell the iPhone in Dubai.
I inherited a new 3g (3.1.2; 5.11.07) that I unlocked before it was ever activated. It came with a factory-installed sim card that i removed. So far everything seems to be working well (don’t use it for calls, so i haven’t bought a non-ATT sim).
However, I cannot use itunes, because i still get the iphone activation/registration screen. Itunes recognizes my device, but it won’t let me transfer music or movie files. I’ve un and clean reinstalled itunes & removed cookies but to no avail. I don’t want to activate and then cancel the original order (not mine to begin with). HELP!!
Okay, i have an iPhone 2g from past use. But am now in the middle of a contract with at&t on another phone. I am able to take out the slot for the sim card and put the sim card from the new phone into the iPhone. But i’m wondering if when i go to iTunes to activate what happens with my new phone? Do I continue paying for both plans? What happens with my “new phone” plan?
hey, I want to purchase a used iPhone 3g from ebay, they guy said it was not unlocked so you needed to have AT&T service. I have AT&T and was wondering if i bought the phone would i be able to just add my sim card to it and use it? i have a data plan on my current phone and wondered if i would be able to just start using it or would i have to go through AT&T again to get it set up?
i just got an iphone 3g and it was restored without the sim card in it X_X , is there any way i can fix this??? I do not have any of the sim card fones, i have verizon. Is there any way i may be able to make it so i may use it as an ipod touch and hacked as well??
i got a used iphone (probably a 2g, it is the model with the metal back) with a sim card. It is unactivated and i just want to use the iphone as an ipod touch with wifi. How can i activate an iphone that is unactivated, without a contract? Thank you
i have a iphone apple 32gs which is locked i dont have the sim card how do i unlock
do i get any info please
You need to jailbreak the phone. Find out whatever the current version of the iPhone software you have, do a Google search for that version and unlocking, and there you go. It’s quite easy, most people can do it.
Hi, I would like to give my daughter my old iphone 3G. She is presently in New Zealand and has a NZ sim card but she also has an 02 sim card on our account here with her. She will be travelling within the next few months to the US and Canada. Should I delete everything off my phone before I send it to her and do you think she will have to use the 02 sim card to be able to use it as a phone, this option could be rather expensive! I presume once she gets to the US she can sign up with AT &T?
Any advice would be much appreciated – thanks
If she’s only going to be in the US for a few months, I would not recommend she attempt to use the iPhone at all as it’s very easy to get hit will bills of thousands of dollars for International roaming and data charges. I would instead recommend she buy a “burner” phone (eg, a TracFone) once in the US.
If you absolutely want her to have an iPhone while visiting in the US she should probably activate the iPhone with whatever the carrier in New Zealand handles the iPhone, then switch temporarily to an International plan while she’s visiting (have her be very careful about data usage though!). Unfortunately, AT&T in the US does not offer a month-by-month plan for the iPhone, you have to sign a two-year contract.
If she is going to stay in the US for an extended time and you don’t mind the two-year contract, then you should delete everything off the iPhone, then have your daughter take it to an AT&T Wireless store in the US so it can be activated and receive a new SIM card.
ok
my iphone is frozen. it gets to the connect to itunes screen, no words, no slide, nothing.
it also, repeatedly keeps cutting off and on.
i cant boot it out
i cant upgrade, or downgrade.
i want to jailbreak, ipod functionality, no service.
i cant live without it.
please help me.
i have the old iphone,,, but i found i 3gs how can i activate?
i have a first generation 8gb iphone. I accidently restarted it, and i really have no clue what to do when it says to connect to itunes and install a sim card. can i put in an at&t sim card while i connect to itunes, and then have it fixed? Or will that just make me pay money. I NEED HELP!!!!!!!!!
You’re going to have to jailbreak it.
do all iphjone 3g’s have a sim card slot and sim if not removed?
iphone* do they have come factory made with sim cards ?
Got me an i phone 3g with 3.1.3 (att) sold from a friend leaving for the US but i dont have the att sim card and it will not take in any other sim card for unlock..Im halfway across the world to get an att sim!what should i do?i want to unlock it so badly! it been lyin around collecting dust =(
You’re going to have to find a way to downgrade the iPhone 3.1.3 software to 3.1.2, then jailbreak it using software like Blackra1n.
Try the comments of this thread for advice (solution may be toward the bottom): Downgrading from 3.1.3 to 3.1.2
My wife has an old ATT plan for $20 a month and no frills. She lost her phone so I was wondering if I could buy a used iPhone and use it on her existing plan. I know ATT requires data or messaging plans for new activations of iPhones. We just want the basic service, wifi and access to the iTunes store from the computer.
My daughter was messing around with my iphone and put her sim card in it, now it won’t turn on at all, or connect to my itunes. What can i do to fix my phone
Do i have to activate my iphone in order to unlock it? If so how would i do that? Please help! ihave downloaded blackrain, snowbreeze, and bought an “unlock” on line. Nothing works!
No, you don’t need to activate an iPhone in order to jailbreak and unlock it. What you do need to do is match the right jailbreak software with the right version of the iPhone’s firmware. For example, Snowbreezer 3.1.3 for iPhone OS 3.1.3.
There used to be an way to check an unactivated iPhone’s version of the OS, but it may no longer work. It was this: Go to the emergency call, enter *3001#12345#* then press Call. Tap Versions and match the modem firmware with the list below:
1.0 firmware has 03.11.02_G modem firmware.
1.0.1 firmware has 03.12.08_G modem firmware.
1.0.2 firmware has 03.14.08_G modem firmware.
1.1.1 firmware has 04.01.13_G modem firmware.
1.1.2 firmware has 04.02.13_G modem firmware.
1.1.3 firmware has 04.03.13_G modem firmware.
1.1.4 firmware has 04.04.05_G modem firmware.
2.0 firmware has 04.05.04_G modem firmware (1st generation iPhones will remain at this baseband level.)
2.0 firmware has 01.45.00 modem firmware.
2.0.1 firmware has 01.48.02 modem firmware.
2.0.2 firmware has 02.08.01 modem firmware.
2.1 firmware has 02.11.07 modem firmware.
2.2 firmware has 02.28.00 modem firmware.
2.2.1 firmware has 02.30.03 modem firmware.
3.0 firmware has 04.26.08 modem firmware.
3.0.1 firmware has 04.26.08 modem firmware. (First time there wasn’t a change in the baseband.)
3.1 firmware has 5.11.07 modem firmware.
3.1.2 firmware has 5.11.07 modem firmware.
3.1.3 firmware has 5.12.01 modem firmware.
Unfortunately, the emergency-call method no longer works. Some jailbreaking software can detect what version of the iPhone firmware you have (PwnageTool for the Mac seems to do this).
If you can’t find out your iPhone firmware version and are desperate enough, I would try a process of elimination. Start with the appropriate jailbreak software for 3.1.3 and move backward from there.
i found an iphone 8gb with the previous sim card in it. i dowloaded ZiPhone and it has an option to jailbreak the iphone. i want to unlock the iphone so that i am able to use it with my current t-mobile carrier. how do i do that? because everytime i try to jailbreak it, it tells me that there is an error, and i don’t know what it might be? itunes syncs it, but for some reason i am unable to jailbreak the iphone. HELP would be appreciated.
-Tannia
I am planning on purchasing the Iphone 4 when it comes out on the 24th. I currently have the 3g. My best friend has the original iphone, and the cheaper plan that goes with it. If i give her my iphone 3g, can she put her SIM card in it and keep her current data plan and still have the phone function properly?
i found a iphone 3g had a at&t sim card in it but i want to put my sprint sim card in it. What can i do to make it work and it is not reading the at&t sim card and its asking for a PUK code thing.
iPhone doesn’t work on Sprint. Sprint is CDMA. iPhone is GSM.
hello, i already have an at&t phone, with no data package. my friend is getting the 4g when it comes out and is giving me their 3gs. can i just put my simcard in the phone? how would i go about upgrading my contract with the data plan as well?
It may work by putting your old sim card in, but the easiest thing to do is take it to an AT&T store and they’ll get you set up. With your old sim card, you may be able to use the iPhone without a data plan for a while, but eventually AT&T will require you to add on a data plan. Its part of AT&T’s terms for the iPhone.
Currently I have a phone with 2.2.1 firmware (also jailbroken). I used to have a plan but I ended it and now it has no sim in it. I want to upgrade to 3.1.3, but to do that, I think you need to have 3.1.3 firmware (unjailbroken) on the phone first. Can I just use sn0wbreeze or do I need to do something else.
I bought a 3GS on ebay, tried to put my OLD Centennial SIM in it but no worky.
Centennial was bought out by AT&T so I’m actually an AT&T customer now.
How can I make my iPhone work without taking it to them, I do not want a data plan, reception is BAD, if I can’t do voice I sure can’t do data. It only works out in my yard, not in the house, not in stores. No need for data and I don’t want to pay for something I can’t use and don’t need. I want to activate the iPhone on AT&T just as a cell phone only, no data. Is there a way to do that?
I also want to jail break it so I can install 3rd party apps. I have wifi at home.
I have got an iPhone 2g and I bought it from a kid at school and I know nothing about him and I no longer have the sim card tht was origanlly in it when I got it from him is there any way I can get a new sim card and activate it tht way (I already have a AT&T line) I need help plzzzzzz tell me what I have to do to use it as a phone
Ps it’s jail broken and I use it as an iPod touch for now
You have two options: Take it to an AT&T Wireless store and tell them you want to use it as a phone. You’ll have to restore it first (removing the jailbreak software) and pay AT&T their monthly due. Your other option is to use it on TMobile. Instructions for how to do this are here:
https://artoftheiphone.com/2010/06/09/how-to-use-an-iphone-without-a-data-plan-voice-only/
i just got a used iphone 3g. i have att with a unltd data plan but not the unltd text. i can get the phone to work but not the data. any advice?
thanks :)
If you’re already paying for a data plan, just take it to an AT&T store and explain the situation. If it’s jailbroken, you’ll have to restore the phone first.
Alan,
I have a question regarding the very last step in a restore process where you need a sim card in the phone before it becomes usable.
I have jailbroken and unlocked my 3G, and am selling it to someone who will be using it on T-Mobile.
Do I need to give him my original (deactivated) sim card in case he ever needs to restore? Or will any sim card you pop in get you through the restore process? I’m just curious, my number is still seemingly linked to it and would prefer not to give it if he doesnt need it. If he will need it – is there anything I need to be worried about?
Thank you.
No, you don’t need to give him the sim card. They won’t even need a sim card in the iPhone in order to jailbreak and unlock it. Once it’s unlocked, your friend will just need to stick the new T-Mobile card inside.
i bought an iphone 3gs and also bought a sim card… but it just tells me that it has “no service” on the top right corner .. is it because the sim card is not the original one? or what?? please help need an answer ..
“on the top left corner”… my bad
I need more info to troubleshoot your problem. You just can’t stick any SIM card into the iPhone. Even an AT&T sim card won’t work if it’s not the right type. Your best bet is as the article above states, take it to an AT&T rep or jailbreak and unlock it for use on T-Mobile.
Can you use a prepaid SIM from an MNVO like Pure Talk USA?
My Aunt gave me her iphone, I decided to erase all content through setting then restore in itunes. However Now when I Sync with itunes Its say please Insert Sim cards,So I borrow my aunts sim card and install it to my iphone then plug to itunes it says non-compatiable. Right Now Im on the slide for emergency screen, Should I jailbreak it?
I have a white 16gb iPhone 3GS and my friend as a Black 32gb iPhone 3GS. He wants my white iPhone + $25 to exchange it for his black one. My question is: can we do this trade and just pull out our respective sim cards and put it in our “new” phones without a problem or do we have to inform at&t? Any advise?
i recievied a i phone and i just want to use it as a ipod. it has no sim card and says the i tunes and the plug and then on the bottom it sasys slide for emergency. how do i get it to unlock so i can use it.
I have an original gen1 iPhone. Recently part of the screen became unresponsive, so a friend of mine gave me an old iPhone they weren’t using. When I try to put my sim card into their phone, iTunes wants to go through new phone activation. Is there any way for me to force the phone to restore from the backup of my other phone without re-upping my At&t plan?
@Meghan
Go through the new phone activation. Then after its completed, keep your iphone plugged into itunes, and then it should give you the option to restore from a backup.
Hi,
I am currently part of my parent’s family plan on at&t, and use a cheap slider phone.
If i were to buy a used unlocked 2g 8gb iphone, can I use it on my existing plan, without adding any new data plan? I would want to just use it as a phone and with wifi.
Thanks, and I would really appreciate a reply.
No, even if the SIM card worked (some AT&T sim cards will work once inserted into the iPhone), AT&T would eventually detect you’re using an iPhone and begin charging you for the data plan. It’s part of the terms of service for connecting an iPhone to AT&T. You’ll have to use T-Mobile for an unlocked iPhone.
I dropped my 3G iphone so my sister in law gave me hers cause she bought a new one. How do I switch the phones so I can set her iphone up on my itunes account? (I have the SIM cards for both phones). When I put my SIM card in her phone and hook it up to my itunes account, it keeps coming up with her name on it.
A friend gave me his old 2G iPhone with the SIM intact. I’ve registered on iTunes and have been using it as an iTouch on WiFi. It’s become really handy and even though it’s old Edge technology, I’m considering activating it using a T-Mobile prepaid plan.
If I replace the SIM with a T-Mobile SIM and activate the phone, will I lose all my apps? What will be the repercussions when I sync with iTunes after the SIM is replaced?
Q: I currently have an iPhone 3GS with an unlimited data and corresponding voice plan. I have the opportunity of purchasing a deactivated iPhone 4 with the micro sim still in the device. The iPhone 4 has previously been activated and used for another account which has since been cancelled (phone also deactivated). Will AT&T allow me to bring the iPhone 4 into one of their stores and use it as a substitute for my current 3GS with my number, data and voice plans remaining intact?
Brian: yes
@Alan (or anyone else who can answer),
Alright, so here’s my dilemma. I’ve been using an iPhone 2G (original) that my friend gave me that doesn’t have a SIM card. It was working fine until I accidentally upgraded the firmware of iOS from 2.2 to 3.1.3. I believe it successfully loaded the new firmware, but now it is stuck on the recovery screen that says “Insert a valid SIM with no PIN lock to activate iPhone”. I have been looking for ways to activate (aka hacktivate?) this without a SIM card since I don’t have current access to one, but I found that the only way to do that without a SIM is to jailbreak it.
However, I’d prefer not to jailbreak because I’d like to test out 3.1.3 without it jailbroken. Also, the MOST important factor to me is that I have notes and calender entries that I’m afraid to lose if I jailbreak.
So my question is, should I jailbreak or borrow my friend’s SIM (he has an iPhone 3GS)? And if I choose to use his SIM, will I be able to put it in just to get past the activation screen, then quickly take it out with no risks (as in none of his data getting on my iPhone)?
Also, if I jailbreak will the notes and cal entries still be there from before I updated the firmware?
Thank you so much to ANYONE who replies, I really really appreciate an answer and any help you can give. :D
Oh yeah, and in addition I have no intentions for using the iPhone with a phone plan (I just want to use it as a touch).
THANK YOU!!!
Please can someone respond? Anyone?? :/
Did you back up your iPhone before you updated? If so, go ahead and jailbreak your iPhone. All your stuff should still be on the iPhone anyways. Upgrading to 3.1.3 shouldn’t overwrite your personal stuff.
i updated from a 3g to a 4 and i restored the 3g not knowing it would lock up. i still have a sim card but im afraid that when i use it to activate it, it will mess up my other plan.
should i activate it????
Yes, go ahead. It won’t mess anything up.
Recently I bought a iphone 3GS with OS3.1.3 with a Roger Sim in it (the phone is from canada and i am in bangladesh). After I have put my local sim inside it was showing invalid Sim. later I went to Singapore and got the phone unlocked came nack to bangladesh and used it without any problem.
However after I have upgraded the firmware from OS 3.1.3 to 4.0.1 again it is showing invalid Sim and I am stuck with it.
My questions are:
can I jailbreak my this iphone with jailbreakme 2 software?
do I need to activate my phone for jailbreaking? or I can can browse thru Wi FI? and load cydia
Please help me
Azimul: You will have to do two things, jailbreak then unlock the iPhone. The Jailbreakme exploit only jailbreaks, it does no unlock the iPhone for use on other carriers. You’ll have to use the latest version of ultrasn0w to unlock the newest iPhone software.
ok so i got a samsung flight with a unlimited plan with pics messaging and my mom just gave me her old iphone can i put my sim card in the iphone and it will work its on ATT
Sometimes putting an ATT sim card inside an activated iPhone works, sometimes it doesn’t. However, note that AT&T will eventually recognize that you’re using an iPhone, and if the cost of your monthly data plan is different from the iPhone’s offerings, your data plan will be changed to the iPhone plans. So, make sure you’re ok with that.
thanks Alan for the reply greatly appreciated.
Do I need to activate my iphone? or just I need to go to any wi-fi hotspot and browse thru Safari to go to jailbreakme.com?
Azimul: My bad Azimul, it turns out you can unlock your iPhone using Jailbreakme.com. After it jailbreaks, it will install an app called Cydia. Use that app to download and install ultrasn0w, which you will use to unlock your phone. After you do that, install the new SIM and enjoy.
I bought a non committal 4G iPhone from an AT&T store in US as a gift for my uncle who works in Dubai. It is not activated. For him to use in Dubai, he said he will have it unlocked and use the SIM from a local carrier. To unlock does it need to be activated first by AT&T? Thanks for any help on this.
I just noticed your column “I Have an Unactivated Used iPhone Without a SIM Card. How Do I Activate It?” Is this true also for brand new (never used) iPhone too? If yes, without activation, is it possible to install and the jailback software? Thanks
Mark: If you’re looking to activate an iPhone without a sim card, it’s called Hacktivation. Unfortunately, software to do this for an iPhone 4 is not available yet as of this writing. RedSn0W is the software you’ll want to pay attention to. Only an iPhone 3G running iOS 4.01 can currently be hacktivated, the iPhone 3GS and iPhone 4 cannot. I’m sure that will soon change. Be patient. Here’s a guide for the iPhone 3G hacktivation.
My son gave me his old 2g iphone which has been completely restored. We do not have the original sim. I did get a new sim from att store and I want to use it as an ipod touch. Is this possible? HOW? I have searched and searched online but with the iphone being restored i have no idea of software version or how to jailbreak. All of the instructions I find online have iphone still working. ???
Our son gifted us a 3GS purchased in Japan with a softbank SIM card. AT&T says he has to get a “code” to unlock the phone from Japanese softbank. AT&T store mgr. installed an AT&T card BEFORE he knew phone’s origins were Japanese. Then he tried to activate; no go. Any other way without losing any of the iPhone’s/Apple’s features short of sending it back to him and having him sell it in Japan?
Softbank will not remove the sim lock on the iPhone, so for the AT&T store manager to say that was ridiculous—he should know better. I suggest you jailbreak and unlock the phone, then try once again at the AT&T store. Jailbreaking and unlocking has been made legal in the US, so you won’t get in trouble. The worst that can happen is they’ll refuse to activate an account for you.
If the iPhone is activated, follow the steps in this video to jailbreak and unlock.
Once it’s unlocked though, don’t do any of Apple’s software updates until you known there is an unlock solution for that version of the software.