Simply replace the unfilled areas such as "[]" and "[date]" with your information.
Dear [name],
Thank you for your recent correspondence regarding your
account number ____________. We were able to track down the error and have credited your account accordingly. A report to this effect has also been sent to our credit reporting company.
As of this date, your account balance is $_____________.
You are a valued customer and we apologize for any inconvenience this mix-up may have caused. If we may be of further assistance please contact this office at your convenience.
Sincerely,
[name]