I don't know much about Cingular but I can tell you that Verizon's customer service is awful! They interrupted my service for nonpayment when I was on call because they messed up my payment and lost it! Even though the whole thing was 100% their fault, it still took a whole day for them to straighten things out and credit my account the reactivation fee!
They also make mistakes on their charges, always in their favour of course.
Very unsatisfied customer here as you can see!