I hereby would like to communicate to you my disappointment related to the Logitech monitor model ERT789000-RE, which I purchased about a month ago in your official store, located at 1503 W 20th Street, Puebla Mexico. Since I bought the monitor, it has not been working properly and It has been intermittently displaying abnormal black vertical stripes. Because of these problems, I have not been able to use it correctly. Even after having verified that the monitor is correctly connected and tested on other computers, the problem persists, so It's no use spending more time trying identify the problem. Therefore, I am requesting that you replace my monitor. [Basically good - just a few changes. Next time, you might want to put this in the Notebook section, which is better for handling this sort of thing.]

This italki Knowledge page will give you the format for your letter http://www.italki.com/knowledge/page/BUSINESS%20LETTERS%20OF%20COMPLIMENT.htm