This type of letter is written to complain about a problem. For example, you bought a faulty product that you’d like to exchange or get repaired, and you are writing to a person who has the power to arrange that.
A letter of this type should consist of 4 paragraphs.
The 1st paragraph should start with “Dear Sir/Madam,” or the person’s name if it appears in the task statement. You should explain in 1-2 sentences what you’re complaining about.
The 2nd paragraph should describe the problem in more detail, state what you are unhappy about, what you did to resolve the situation and how you feel about it. This should be the longest paragraph of the entire letter.
The 3rd paragraph should state what kind of actions you expect the person to take, and what you are prepared to do if they fail to resolve the problem.
The 4th paragraph should close the letter with a sentence similar to “I am looking forward hearing from you.” Then write “Yours sincerely” or “Yours faithfully” or just”Best Regards” which is very popular, and your name.