Have you ever received a disconnect notice for owing a balance of $0.00? Rich and Alisa got one from Comcast. They're not quite sure how best to resolve the problem. The entire letter is posted at Consumerist. Commenters suggested sending a check for $0.00, or sending a check for a few cents and then demanding a refund. Link -via NYC Educator
I had the same experience, a negative bill from MCI that for whatever reason managed to become a postive. So I ended up having a credit of $40, to owing $40. When I complained, they refunded me $40! Then I had to explain in great length why they still owe me another $40 ...