My iPad has been showing "no service" or "searching..." in places where I used to get a passable LTE signal from AT&T. But my iPhone 5 is able to find a signal in the same places. I don't understand why. Could it be a hardware or software issue? I know AT&T is bad and that it is particularly bad in Chicago, but I stay with them for personal reasons. So please don't tell me to solve the problem by switching to Verizon. Thanks in advance.