How to write a complaint letter

Hiii... tea-coffee writing time!!
Today we are revising some structures to deal with everytime you are requested to complain about something...
https://www.box.com/files#/files/0/f/0/1/f_6995256276
In case you want to read further click on the following link:
http://www2.elc.polyu.edu.hk/cill/eiw/complaint_letter_constructor.htm