I recently purchased a factory unlocked AT&T iphone 4s. I originally planned on using it with tmobile but I have tried everything and continue to get no service. I went to the apple store (HUGE waste of time) and called AT&T and they said the phone has been blacklisted so phone wont connect to any network, they wouldn't tell me why. The funny thing is that the iphone still works with AT&T. It's currently running on 6.1.2 but is there anyway I could use it on tmobile? BTW I do get the itunes successful unlock screen when I restore.