Dear ***,
I am so sorry to trouble you but I have something important to tell you about your restaurant.
Last week I had a meal in your restaurant.To my anger,the waiter there were so rude that I can not help telling you.What was worse,when charge me the meal,she even charged me more money than necessary.This is where I can not tolerate.In my opinion,as a servece,one must first be careful enough.I don't know why a person like her could be chosen as a waiter.I am here waiting for your answer
Ok,that is all,I am sure you will manage it well.
yours