I've upgraded my iPhone 3GS to iPhone 4 (and my wife's as well). The new phones came with their own US/AT&T microSIM cards and have been activated. So we still have our old phones with the old SIM cards in them. I've deleted the data off of the old phones, and I would like to sell them.
What do I need to do to sell the old phones? Do I remove the SIM from the phone and expect the buyer to put their own SIM in there? How do they go about getting a legit SIM from AT&T to put in the phone? Or do they use the SIM that is in there? How can I be assured the old phones cannot be linked to my current account in any way?