AT
Favorite Answer
What did you do? If it was really bad you need to apologize in person. However you can also use something like this-
Dear sir or mam,
I am writing this letter to apologize for my behavior on (insert date). There is absolutely no excuse for me to (insert what you did) and it will not happen again if you will see fit to let me back in your place of business.
Sorry again,
(your name)