Dear (Mr., Mrs., Ms.) followed by last name
Body of letter
Briefly explain the reason for your letter in the first sentence.
In the main body of your letter, explain the problem, when it happened, along with any other pertinent information. Describe the problem in detail, giving names if necessary, and any information that will assist the recipient in resolving the issue. The more information you can offer, the easier it will be for the recipient to resolve the issue.
Close by thanking the recipient for their time; tell them you look forward to an expedient solution.
Sign your name directly above the typed signature. You may also want to include your name, address and contact information at the top of your complaint letter so that the company can contact you. If you have letterhead stationery, use it; otherwise, type this information on the left-hand side of the page at the top, or center it across the page as a header.