第一段需写写信的目的以及自己的一个概括的期望：常用套话比如I venture to write to complain about ……+定语从句;I would be grateful if you could do anything necessary to solve the problem facing me.
第二段阐述两、三方面所面临的产品或服务的问题及后果：there are several aspects underlying this complaint. For one thing,......For another,......In addition,......
第三段给出具体的期望，比如退款或更换新产品：It is my sincere hope that you could give me full refund or replace it with a new one. Your kind reply to this letter at your earliest convenience would be very much appreciated.