The problem with AT&T is that their service is awful. I never had any real problems with dropped calls, large dead zones, etc., until I got AT&T service. At least I'm not paying for it.
I love having to call people back because the phone decides to drop the call in the middle of it. We have an antenna in my room (it is right above my boss' desk) and I still have the signal drop for no reason, while others are still at full strength. I got a new phone and the problems aren't as frequent, but they still exist. AT&T service just plain old sucks. At least I'm not paying for it either.