How To Write A Complaint Letter Against An Employee . 5 complaint letter sample for everyday use complaint letter sample for poor service. So, when writing a letter complaining about manager behavior, you need to ensure that you have your name, address, the name of the manager and the account of events laid out. Grievance Letter For Wrongful Termination Sample from webcas.org Your name, address and contact number. What to put in your grievance letter. If you've fretted over whether to even complain, you might mention that in your opening paragraph.