Having AT&T as a vendor is much like being robbed by your cleaning lady every month. AT&T has overbilled me as much as $4,000 and drug their feet for months on resolution. That is, until I called to cancel service. Then it was correctly resolved in 10 minutes! Of course, they overbilled me the very next month, so it was hasta for me.
But AT&T is the only company to ever send me to collections for a contract I didn't even sign! My son wanted me to co-sign for an iphone. After reading the terms (that made it pretty clear it was MY contract, not my son's) I refused to sign. A year later, I started getting calls from the sleaziest collection agency I've ever seen, and when I got to the bottom of it, it was for the contract that I'd refused to sign!
Friends don't let friends use AT&T!