The correct option is D I hope that you kindly look into the matter...
The question describes a situation for which you have to write a formal letter.
Formal letters are written in a certain way, their language is a bit different from what we use on a day-to-day basis, like with friends, teachers, colleagues. So, the correct option must be suitable to use in a formal letter.
Option A: This line 'you need to do something' sounds a bit casual as well as impolite. While writing a formal letter, one must be as polite as possible.
Option B: 'Must go now' is very much casual, this is used for informal communication.
Option D: This line does not meet with the said situation. The person who writes this letter is not satisfied with the services, so he is not looking forward to go there again.
Hence options A, B and D are incorrect.
Option C is correct because it is the most suitable option with respect to the situation: the language is formal and polite.