Warner Robins, GA
My family recently changed from AT&T to another wireless carrier because:
AT&T changed our data and internet access plan without our knowledge or consent, and refused to restore it when we complained. In addition, frequent "bearer not available" messages and related no data service were often the case, preventing reasonable and reliable use. AT&T is still GSM/EDGE in our area.
What was unusual was that our service plan dated back to the early days of conversion from analog to digital, and originally was part of a DOD contract plan. The data plan charged for minutes used, not the amount of data. Our original analog phones had data and fax capability via a serial interface cable, as did the replacement GAIT/GSM phones. (Until AT&T (Cingular) killed the fax capability.) They also locked out the ability to use analog roaming in areas without digital(GSM) service. This was a real killer, as large northern parts of our state still have analog service only, due to small independent carriers and the mountains.
What we suspect, and have no way to prove, was that AT&T deliberately killed the old data plan, hoping that we would allow them to convert the account to the current plans, costing far more and not including tethering.
When all was said and done, all of the family's cell phones were replaced with unlocked, non carrier bound, tether capable 3G phones, used on a non AT&T provider. I was hoping to wait for about two years longer before doing this, as by then at least 3G should be available in the area.
I rated AT&T lower than "dirt" on the usual departing customer phone survey. Constant customer service problems, in addition to the problems mentioned above were cited.