I have a pre-ordered T-Mobile iPhone 6 arriving on Friday (full price, direct from Apple). I understand from previous threads that it will be unlocked, but I wanted to establish the exact steps for using this phone on AT&T, since this will be my first experience bringing my own unlocked device to the carrier. The steps below are what Ive gathered from other threads. Can anyone with experience with this confirm? Back up old iPhone (an iPhone 5, in my case) through iTunes. Remove AT&T SIM from old iPhone. Remove T-Mobile SIM from iPhone 6. Connect iPhone 6 to computer (with no SIM), turn on iPhone 6, and go to iTunes. From iTunes, choose Restore iPhone and choose to restore the iPhone 6 to factory default (expect a Congrats, your phone is unlocked message upon completion). Turn off iPhone 6, put SIM from old iPhone into iPhone 6. Turn iPhone 6 on and go back to iTunes. From iTunes, choose Restore iPhone and choose to restore the iPhone 6 to the backup created from old iPhone in step 1. Does this seem right? If so, two additional questions: Does it matter that my old iPhone is not yet unlocked? It comes off contract on September 23, but since I will have an unlocked iPhone 6, I trust I can still move the old SIM into the new, unlocked phone. Do I need to let AT&T know the IMEI for my new phone at any point? Does it matter to them that the SIM is going into a different iPhone? Thanks for your help! I hope this info is useful to others taking the unlocked plunge as well.