To write an effective complaint letter, describe the problem clearly, include key dates, and specify the time frame for getting a response. Include your name, address, and contact email or phone. Be friendly but authoritative, concise and factual.
Address the letter to the customer service department or the manager, and name the product or service you are dissatisfied with at the reference section. In the body of the letter, state the problem you would like the other party to solve. Give details of the purchase date, when you identified the problem and any steps you have taken to solve the problem. Note any people you contacted, the efforts they made and the results. Attach any available supporting documents, and explain the actions you plan to take if the other party fails to address the complaint.
Be concise so the other party can understand your letter quickly. Use proper grammar, a complimentary tone and an organized layout to establish your credibility. Use facts to enable the reader see relevant dates, details and requirements immediately. Avoid writing a sarcastic or threatening letter as the person reading the letter may not be responsible for the fault. Suggest what the other party should do, and be willing to wait as he solves the problem.