Why this is not band 9 letter?

[saqibali]

Formal letter: 
Subject: "You recently went shopping at the local supermarket. When you got home and studied your bill you found that you have been charged for items you did not purchase. 
Write a letter to the supermarket manager explaining what has happened. Tell the manager how you feel about the error and ask him to do something about it." 

Dear Manager,


I am writing this letter to inform you about ambiguities in your grocery bill and to ask for corrective action.Please allow me to explain what happened to me yesterday.

Last night, as usual, I dropped at your shop to purchase my weekly grocery items for my home.Since I trust your services and since I have been purchasing from your shop regularly, so I did not bother to check details of your machine generated bill.After my return at home, accidentally,I skimmed details of the bill and surprisingly, I found many prices of items that I did not purchase.

This has shattered my trust on your services as I never checked my previous bills.I have this bill in my home.I will ask you to send a representative to collect the receipt from my home and send me the extra deducted money as well as issue me a corrected bill.

Waiting your hopeful reply,

[Damien P.]

Formal letter: 
Subject: "You recently went shopping at the local supermarket. When you got home and studied your bill you found that you have been charged for items you did not purchase. 
Write a letter to the supermarket manager explaining what has happened. Tell the manager how you feel about the error and ask him to do something about it." 

Dear Manager,


I am writing this letter to inform you about ambiguities in your grocery bill and to ask for corrective action.Please allow me to explain what happened to me yesterday.

Last night, as usual, I dropped at your shop to purchase my weekly grocery items for my home.Since I trust your services and since I have been purchasing from your shop regularly, so I did not bother to check thedetails of your machine generated bill.After my return at home, accidentally,I skimmed details of the bill and surprisingly, I found many prices of items that I did not purchase.

This has shattered my trust on your services as I never checked my previous bills.I have this bill in my home.I will ask you to send a representative to collect the receipt from my home and send me the extra deducted money as well as issue me a corrected bill.

Waiting your hopeful reply,

Your letter is good.
Nevertheless, it might have got less than 9 for some reasons:
- 1st body paragraph:repetition of "since" and succession of "since" + "so". Better say "Since X is red, Y is green" or "X is red, so Y is green".
- You repeat the word "bill" 5 times throughout your tex and "home" 3 times, two of which in consecutive sentences.
- If you do not know your interlocutor, you might use "To whom it may concern" at the beginning and "Yours Faithfully" at the end, although I am not 100% sure about the importance of that element on your band score.
- You punctuation might be exaggerated sometimes, even though you are perfectly clear and concise. "After my return at home, accidentally,I skimmed details of the bill and surprisingly, I found many prices of items that I did not purchase" could become "Back home I skimmed through the details of my bill, and surprisingly found unpurchased (or undesired, depending on the exact meaning) items". This correction is very subjective, by the way.

[saqibali]

Anyone who can
Spot the grammer mistakes?
Challenge my task achievement?
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Suggest better variety of words and phrases?
Suggest better cohesion?
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