I called someone at a local Cingular store, and he said he couldn't help me. He advised me to call the automated lines again and just randomly enter a long series of numbers, which he thought would eventually hook me through to an actual customer service representative. I tried this, and was eventually put through to a real person.
She thought that perhaps Cingular might have my number incorrectly listed on someone else's account as a home number, but they are not able to look up accounts based on home numbers so she was unable to help me resolve the issue in any way.
I asked if there was an IT department it could be escallated to, or anyone who could help me, and she said the best she could do would be to write up a ticket for my problem. She did so at my request. We'll see what/if I hear back from them.
In the meanwhile, to temporarily soothe my rage at my helplessness in this situation, I've filed a complaint with The Better Business Bureau. I've also attempted to file a complaint with the Do Not Call registry, with whom I listed my cellphone several months ago, but keep getting a message indicating that the site is down.