Respuesta :
I am dissatisfied with the service. In the sentence it put how she feel about the service at the end while in this sentence how she feels is near the beginning of the sentence.
I am dissatisfied with the service I received.
This is the better revision because the word choice is more specific to the topic of the letter. Also, the more professional tone distances herself from the manager and gives more her more authority. The original sentence sounds too informal. This would be problematic because the audience of the letter may see the author as whiny and complaining instead of a person who should be taken seriously and worth listening to.