Formal phrases: There seems to be a mistake

Formal phrases:
There seems to be a mistake.
I took the book back to the shop.
Please send me a replacement.
I returned the book to the shop.
I have put in the money.
I have enclosed a cheque.
Give my regards to
Please would you give this matter your immediate attention.
Please confirm the arrangements.
I am enquiring about
I am enclosing my application form.

Informal phrases:

I got your letter.
You are wrong.
I want
I would like a new one.
Give my love to
I would like
I want this sorting now!
Straight away
I need
Let me know if it's not OK.