Do you make your complain in person or write a letter of complant?

I would first make a complaint either in person or by phone because discussing the problem directly might quickly resolve it. If I didn't receive satisfaction that way, I would then make a formal written complaint to the company. When dealing with complaints and problems it is well to consider both sides: the problem may be due to a fault or misunderstanding of your own; it may be due to faulty equipment which the shop was not aware of or it may be due to genuine bad service. Usually you cannot tell at first what the real reason for the problem is and it pays to approach a complaint in the spirit of discussion and fact finding first. This way you will ensure that the dealer is not antagonised and will be more likely to help you to solve the problem.