suppose your customers complain about late delivery, how would you reply nicely?

Sorry to hear that you are not satisfied with the late delivery. We understand that timely delivery is very important to you. We have investigated the reasons for the late delivery and have taken measures to prevent it from happening again. We are committed to providing you with the best service and will do our best to make up for the delay. We sincerely apologize for the inconvenience caused to you and will continue to work hard to improve our service quality. If you have any questions or suggestions, please feel free to let us know and we will try our best to help you.