How To Write A Dispute Letter To Insurance Company . Additionally, you should include any documentation connected with the incident along with photos, police reports, or other information. This letter is especially used for credit reports. Letter Of Medical Necessity for Physical therapy Template Samples from simpleartifact.com Start the letter off by date, name of the insurance company and their address. The letter should be sent by certified mail, so the customer has proof that it was received within the time limit for a dispute. Dear sir/madam, i am writing to request an investigation of the following;