[Your letterhead, if desired; if not, your return address]
[Date of letter—month, day, and year]
[Recipient's first and last names]
[Street or P.O. box address]
[City, State ZIP code]
Dear [recipient's name]:
I am writing to apologize, on behalf of GHZ Technology, because I understand that you were not satisfied with the quality of the computer keyboard that you purchased from us on March 11, 2011. We would like to make amends for this matter, so we will be sending a new keyboard (the same model and style that you purchased) to you within the next 7 days. The keyboard will be shipped via UPS, and upon shipment you will receive an email that includes the tracking number.
If you have further questions or need additional assistance with this matter, please do not hesitate to contact me. Thank you for your business, and again, I apologize for the inconvenience.
[Sender's first and last names]