HT1976: iOS: Understanding cellular data networksLearn about iOS: Understanding cellular data networks
Currently Being ModeratedJun 3, 2013 8:08 PM (in response to Storkrnc)
Replacing the SIM cannot possibly resolve the issue. For what reason would you take the device to the clowns at AT&T?
Apple provides all warranty and support service in the US. Take the device to Apple for evaluation and replacement.
The missing IMEI indicates a serious hardware failure.
Currently Being ModeratedJun 4, 2013 6:37 AM (in response to Storkrnc)
That's a critical failure, usually (though not always) caused by jailbreaking or hacking the phone. It can not be fixed. It will need to be replaced.