Stop wasting your time trying to reach them.
Send off two notes: One to your State's Public Service Commission, and one to your State's Attorney General.
Make it short and sweet.
Depending on which state you're in, the reaction will range from them simply attaching (the equivalent of) a Post It note and forwarding it over to AT&T/SBC, and forgetting about any further action, up to .... some extreme nastiness.
Even if it's just the former, though, it _will_ get the attention of someone useful at AT&T/SBC.
Oh, for good measure, you can also send a similar letter to the FCC and the FTC.
(There is _plenty_ of ugly history regarding improper billing by telcos, and the AGs - at least in the states that care ... - are well aware of it).
_____________________________________________________ Knowledge may be power, but communications is the key email@example.com [to foil spammers, my address has been double rot-13 encoded]