Rips off loyal customers!!!

I cancelled my AT&T U-verse account in August due to relocation. AT&T has continued to bill me for 2 more full billing cycles. Owing me over $350!! I have called AT&T over 10 times to have this issue resolved and the adjusted credit posted to my account. Now, AT&T has suspended my wireless services because of an amount owed for less than the credit amount they owe me!!! If they would get their act together, the credit would have been posted to the account (as promised several times, even with confirmation number!) and my services would not be suspended or past due! I refuse to pay more to them, while they owe ME money.
I have been a loyal AT&T customer for over 15 years. These untrustworthy, negligent action are not what a faithful consumer expects. Sadly, it seems it is time to seek services elsewhere!