Just adding one more voice to this thread. I am also in Ohio on AT&T.
I have done absulutely everything discussed in this thread: regular device restore, new sim card from AT&T, got new iPad replacement from Apple, set up as NEW device (did not restore from old iPad 1 backup), turned off LTE (which helps but you should not have to do this). I've been to Apple twice, talked to AT&T 4 times, they both blame the other.
There is only one thing I have not tried: a DFU restore. Had anyone out there tried this? I have not only because I don't want to set up my device as "new" again with all of the configuring that has to be done afterward.
The DFU restore supposedly restores the firmware and the software on the iPad. Just wondering if anyone has tried this before I do?
1. Close iTunes.
2. Connect your iPhone to your computer and then launch iTunes.
3. Turn your iPhone off (hold down the power button at the top of the iPhone).
4. Then, hold down the sleep/wake button and home button together for EXACTLY 10 SECONDS, then release the sleep/wake button.
5. Continue to hold down the Home button until a message appears in iTunes telling you an iPhone in recover mode has been detected. When you are in DFU mode your iPhone screen will be completely black. Remember that if you see the restore logo, iTunes logo, or any message on the iPhone screen, you are not in DFU mode but standard Recovery Mode.
6. Hit the OK message that should popup to restore your phone.