When writing a letter of complaint its important to?

Address your letter to someone at the top: the president of the company, the vice-president, or someone else with the authority to help you.

If you have been a loyal customer of this particular company, say that.

Briefly state your complaint. Do not attack the company or any of its employees. Do describe any actions that contributed to your problem.

Propose a solution. If, for example, you had an auto repair that wasn't satisfactory, you could request a refund or ask that the repair be properly done.

If possible, close on an optimistic note. For example, you could say that Company X has a fine reputation for customer service, so you are confident that your complaint will be resolved in a positive.