AT&T (SBC Global) email admins?

I hate going this route, but repeated attempts at all other avenues have been exhausted. We have a customer IP that has been blocked from sending email to SBC Global addresses since day one. The options AT&T has presented for dealing with this clearly have no effect or simply don't work (one of the email addresses bounces). Could someone contact me privately and clue me in as to who can be contacted to clear an old blacklist entry? --TimH