Courtesy Letters
Use a Courtesy Letter to advise vendors that you are contesting a charge on one of your accounts as indicated on one, or more, of your current credit reports. Request that they contact the appropriate credit reporting agency and correct the error.
A courtesy letter is just that. If disputing an error with a company that there has been a long standing relationship with and wish to maintain that relationship then use this letter. There is also no reason to send it certified, unless you want to document everything.
