Writing a letter of Complaint (it just 3 paragraph ) You just bought a 10-speed bike. The brakes keep sticking, the gears don't shift smoothly, and the pedals keep falling off. What should you do? First, decide what you want? A new bike or your money back?If you went to the manager and your problem is not solved it's time to write a letter of complaint. An effective letter of complaint is: Neat, brief and to the point. Be sure to include your name, phone number, and important facts. Important facts include when you purchased the bike, cost, model or serial number, manager's name you spoke and dates. State the solution you want to your problem and how long you are willing to wait.