Actually, I didn't think SBC had that bad of a reputation compared to some of the others in the industry. I always assumed they went with the more recognizable brand name. Of course, you have to laugh at the irony of AT&T selling off their wireless division to Cingular only to have Cingular become part of "The New AT&T" a few years later.
Maybe you just confused Pacbell with BellAtlantic. BA didn't exactly have the best reputation.
I have seen some smaller Telcos changes names for apparently that reason