Hmmmm. I've been with AT&T for about 5 years as they are the only company that actually allows a signal "here and there" in the suburban foothills of Boulder, CO, where I used to live. No issues, and I am pretty anal with my oversight of my bill.... I kept them when I got an iPhone, after having moved back to NM. Coverage not as good as some others here, but works at home and works at work, so I am reasonably happy.
I also work (in my spare time) for a nonprofit that chose AT&T for long distance on the land line. A sweet Israeli made some calls to the homeland on our line, unaware of our long distance plan (no international calls!!), and we were charged a ridiculous amount. I can't remember, but it was at least $3 minute. However, the charming rabbi talked with AT&T and got the majority of the bill reduced. I don't know if this was due to his charm or the customer service of AT&T. However, I can say: I have had NO issues with AT&T. As long as you are clear on the service they are providing, including fine print, they have been fine by me.