投诉信是我们生活中常见的一种书信形式，可以用来向有关部门或单位反映自己的问题或不满。下面是一篇关于投诉信的英语作文。

Dear Sir/Madam,

I am writing to express my strong dissatisfaction with the quality of service I received at your restaurant last night. I visited your establishment with my family and we were extremely disappointed with the overall experience.

Firstly, the food we ordered took an unreasonably long time to arrive at our table. We waited for over an hour and when the food finally arrived, it was cold and unappetizing. Secondly, the staff were unprofessional and unhelpful. They showed a complete lack of interest in our needs and repeatedly ignored our requests for assistance.

Furthermore, the cleanliness of the restaurant was also subpar. The table we were seated at was dirty and the floors were littered with food debris. This not only detracted from the overall ambiance of the restaurant, but also raised concerns about hygiene and sanitation.

I believe that as a paying customer, I deserve to receive quality service and a pleasant dining experience. I hope that you will take this complaint seriously and take immediate steps to address the issues mentioned. I look forward to hearing from you soon.

Sincerely,

[Your Name]