Chad P
If you are worried about your credit rating I believe that a written letter saying you dispute the bill puts them in a bind vis a vis reporting to the debt rating agencies. I believe it is the fair debt collection practices act has provisions for dispute of a bill and prohibits a creditor from reporting an unpaid bill if it is in dispute. I am not sure specifically how the dispute provisions work (i.e. what hoops they must show in order to report you once disputed) but i'm sure a google search could shed some light on the subject.