I purchased a 16GB iPhone 5 using my upgrade this morning from Best Buy, bought it right off the shelf (well the locked closet). The phone has never been opened and the guy at Best Buy only activated the SIM which deactivated the SIM in my 4S. My question is, before I sell the phone should I open it and fully activate the phone itself? Since it wasn't purchased from Apple or AT&T how would the phone know which account it needs to be activated for? I understand I can easily deactivate the SIM, but can I sell it unopened without the buyer having any issues?
If you were keeping your old phone, and your were selling the new phone to another AT&T customer, couldn't you go into an AT&T store AFTER purchasing the new phone and request a new SIM card for your current phone, effectively deactivting the SIM associated with the new phone?