I sold my new AT&T iPhone 4s to someone on eBay, unopened. It was ordered as an upgrade from apple.com. They received it and took out the sim that came with it and plugged in their t-mobile sim. I informed them at this time that phone cannot be unlocked and used with t-mobile, they knew that, they just want to use it as an ipod touch untill the unlock comes out. So how can they use the phone? So in the meantime the say they can't use the phone unless they have my at&t billing zip and last 4 of Social. If they enter this I am afraid my service is going to transfer to the sim card that came with the new phone. They are claiming they have to have this info to use the phone at all, EVER. What do I do? Can an at&t store make it work?