What should I do if a customer is not satisfied with my initial response to their complaint?

If a customer is not happy with your first answer, it is important to do something about it. First, say that you are sorry and that you know the customer is not happy. Secondly, say that it is your problem, even if it was not your fault. Thirdly, try very hard to find a solution that will make the customer happy. Lastly, show that you understand how the customer feels.