Does AT&T blacklist phones? I plan on selling some old phones, but am wondering if AT&T blacklist phones. My issue is I have an iPhone 4 and a 3GS i want to sell to pay off my bill for my iPhone 5. AT&T currently cut my line until I pay my bill, so I'm wondering if they blacklisted my old phones. My 2 year contracts on the other phones have been completed, the only contract I have with them currently is for the iPhone 5. Both are cim card phones, and the iphone 4 is gsm. Will the buyer have any problem activating the phones with AT&T considering the contracts for those phones have been completed except for my current contract on my iPhone 5. Thanks.