【正确答案】[参考范文]：
Dear Sir or Madam,
I' m writing to complain about the poor quality of an air conditioner that I purchased from Sun Appliance Company.
Frankly speaking, Sun Appliance has always been my favorite. The machine operated well at first, but ten days later, there was a fault that bothered me, that is, the fan made much noise that I could not sleep at night. Its poor quality ruined almost all your image in my heart. I strongly suggest that a repairman or a service engineer should be sent to my home without delay. I wonder if you could pinpoint the cause of the malfunction as soon as possible. If you can't, I am afraid that I will request for full amount of refund or a new air conditioner.
I would appreciate all your assistance in this matter. If you have any questions, please don't hesitate to contact me. Look forward to your reply.
Sincerely Yours,
Li Ming