how to write a formal complaint letter.
Start with a greeting, such as Dear….
In Paragraph 1, state the reason for writing, for example: I am writing to complain about….
In Paragraphs 2–3, describe what went wrong using phrases like Unfortunately or Sadly.
Then, in Paragraph 4, give suggestions for improvement, such as I feel that you should improve/change/make sure….
In Paragraph 5, make a request for compensation, for example: I believe you should give me a refund/an apology.
Finally, end the letter with a closing sentence, such as I look forward to your reply. Yours faithfully, [Your Name].