I have a 3G iPhone that I have had since July and its been unlocked since I have owned it. It is running 3.1.2. I was cleaning my house today and found an old sim card so I put it in the iphone to see if there were any old numbers on it I needed. It wouldn't read it so I put my old card back in and it now won't read that. I tried my girlfriends sim and it wont read it either. I have put my sim in another tmobile phone and it works fine. I have tried to hard start it, restore from a backup, sync, and restart it. I have blown into the sim card tray to try to clean it out of dust and I have wiped down the sim card. Nothing is working, and it is out of warranty. Anyone have any suggestions?