It's all a matter of documentation and patience. The process might turn your hair gray... it all depends on how easily the phone company wants to make it.
Have proof that you never lived at that other address - like other utility, credit card, or misc. bills showing the correct address. Contact the other address and see if they have a correct address for the Marc(k) Johnson they have listed and provide that to SBC.
You'll have to have the patience of Job and the tenacity of a shark to get this fixed. Be ready to write several letters and be sure to demand letters stating the corrections from both SBC and the credit reporters.