I recently reported an issue I was having with Cingular Wireless. I still have their former AT&T service, and I now don't get signal in many parts of central Austin. Surprisingly, customer service officially created a "ticket" for the issue. Even more surprisingly, they followed up the same day with some questions and are, according to policy, following up every seven days.
Cingular's policy doesn't guarantee they'll fix the problem. It doesn't even imply the people actually working on the issue take it seriously. But communication helps.