Greetings. My name is CM and I am from S. I am writing you this letter to let you know a complain about the service of your shop.
The term "complain" in this sentence is grammatically incorrect. Any word that follows an article such as "a" or "the" should be a noun. The word "complain," however, is a verb. "Complain" should be replaced with the noun form of the word.
However, I bought a radio from a local branch of your chain shops but the sound of the radio was not clear at all as it seems there are some problems in the sound boxes.
I agree with dumi that the serial number, reciept, and date should be included with this imformation. Also, the term "however" does not make sense in this context and it should not be used.
To get a solution of this problem I contacted in your shop and explain the problem to one of the staffs.
The sentence should be re-written as "To get a solution
of to this problem I contacted
in your shop and
explain explained the problem to one of the
staffs staff." Keep in mind that although the term "staff" (in most cases) is a singular noun, it refers to a group of people. Also keep in mind that although it is considered correct to use the term "staff" as I use it, there may (or may not) be some places where it is acceptable to use the term "staffs" as you used it.
The staff took it back and said that they would repair it soon but I have waited a week and still it is not ready.
As I mentioned earlier, although the term "staff" is a singular noun, it refers to a group of people. As a reader it sounds to me as if several people took it back. I'm not sure whether or not this is intentional. Did one person take the radio back? Or did several people take the radio back? If only one person took the radio back than you should clarify that only one staff member took the radio back.
Also, although the phrase "still it is not ready" has no errors whatsoever, the phrase that most (but perhaps not all) native english speakers would use is "it is still not ready." (If it were conversational English the phrase would be "it's still not ready," but because this is a formal letter the contraction "it's" would not be very appropriate). It is up to you which variation of the phrase you would like to use, as they are all technically correct.
I already called in the shop 3 times and visited once.
And now I am very much disappointed onin the services of your shop.
Whatsoever, now could you please give me an explanation as to why this delay is happening also let me inform me how long it will take to get it back from the shop.
In addition to the corrections noted, this sentence should either be broken into two sentences or made into a compound sentence. It should also have a question mark at the end. However, if you take out the words "could you" the statement will be imperative (give a request) rather than interrogative (ask a question) and the sentence would then need to end with a period.
Finally I want to say that please repair the radio as soon as possible or replace the previous radio with a new one and send me back in myit to the address that I already provided in your shop's register book.
It's redundant and excessive (in my opinion) to begin the last sentence with "Finally I want to say." With formal letters especially, it's best to be as short and concise as possible.
That is all... I hope my comments make sense.
