Dear Mr/Mrs/Ms (name),
This letter is the acknowledgement of your letter and photocopy of your check, which proves that your account has been balanced. We apologize for any inconvenience this may have caused you. Your proof of payment will allow us to go through our systems’ records to figure out where the issue occurred.
We apologize for the letters we have sent you under the assumption that no payments we made on your bill. I know that this misunderstanding must have been disappointing for you as one of our valued customers, one who promptly paid their bill.
We appreciate your patience and assure you that we are doing everything to ensure that this type of misunderstanding does not reoccur in the future.