Response To Complaint Letter

First of all, let me express my sincere apologies for the unintentional mistake and the inconvenience caused thereafter. These incidents are not typical of us and we are disturbed about this as much as you are.

I have ran a quick investigation to find out the reasons that led to this error and I came to the conclusion that it's due to [state the reasons here. Make it short]. This is clearly a mistake at our end and we take responsibility for it.

In our best efforts to keep our customers happy and satisfied, we are going to [give you a new item, refund your money, etc…]. This is the least that we can do in the light of this unfortunate event. We strive for your satisfaction and we want to ensure a gratifying experience for all of our customers.

I would also like to inform you that we will take extra measures to make sure that such errors don't happen again in the future.

I apologize again for the inconvenience.