Someone wants to buy my iPhone 3G 16 GB and he wants to use his carrier - TMobile. My iPhone is jailbroken right now, but I did so to get Cydia apps; my carrier is ATT. Will it be possible for the person possibly buying my iPhone to use his carrier, and if so, what steps will need to be taken to make this happen? Do I need to do additional jailbreaking so that a different carrier can be used? Also, my 2-year contract ends with ATT on 7/11/10 and I am eligible for an upgrade.