Dear Mr. Harding,
I am writing this letter specially to apologize to you due to the error in quantity of the shoes we sent. We have sent you the rest of the shoes you ordered today.
I have acknowledged that my fault has brought you great trouble. I hereby express my deep sorry for this matter.
I promise that this mistake will not happen again. And I would appreciate very much if you could give us a chance to show our sincerity on this matter.
ED 公司 谨上