投訴信是針對某件不快樂的事情向相關負責人提出的投訴、抱怨等的信件，寫作要點主要包括以下三點：首段開門見山，說明寫信目的；?第二段清晰、簡潔描述問題或事情經過，並指出事件給妳帶來的不便；?第三段結尾感謝對方關註妳的投訴，並表明妳想要的解決方案，期待對方盡早答復並解決問題。
1. 首段開門見山，說明寫信目的。
I am writing to inform（告知）you that I find…unsatisfactory…
I am writing to express dissatisfaction/ disappointment/ concern regarding/ with ……
I am writing because I need to complain to you about ……
2. 第二段清晰、簡潔描述問題或事情經過，並指出事件給妳帶來的不便。
I strongly request that a satisfactory explanation should be given.
I am looking forward to your reply at your earliest convenience（在您方便的時候盡快......）.
I would be grateful if you could send me a replacement（替代方案）.
3. 第三段結尾感謝對方關註妳的投訴，並表明妳想要的解決方案，期待對方盡早答復並解決問題。
To solve this problem, some remedial actions should be taken before things get
worse.
To solve the unpleasant matter, I suggest making the following changes.
I shall be grateful if you could consider my situation and improve it as soon as possible.
I trust you will take my complaints seriously and look forward to hearing from you soon.
I understand you will give immediate attention to this matter and reply at your earliest convenience.
英文書信格式