I bought an officially factory unlocked iPhone off of eBay and YES it was factory unlocked NOT jailbroken so DON'T say it is fake because it came to me on iOS 5.1 and I updated it with iTunes to 5.1.1 and it STILL worked. About a week later I wanted to turn it off for a night. The next morning I turned it on and it said No Service. I then toggled the airplane mode settings and it said Invalid SIM and SIM failure. Can someone please help me? My modem firmware is 05.16.05 and it says Carrier: AT&T 12.0 but I have a T-Mobile SIM in and the iPhone came with an AT&T SIM card I needed to use when I first it to activate it during initial setup.