Dear [Name of the Customer]
We kindly ask you accept or sincere apologies for the inconvenience cause in respect to [the issue/ i.e. delivery of product/quality/wrong item dispatched etc.].
We invest high efforts in ensuring our customer’s satisfaction. In this case unfortunately, we did not meet your expectations. After careful review of the situation, we narrowed the cause to [explain the weak link: key staff changes, recent internal system update, office relocation, etc.].
As a testament to our strive for perfection, we have taken steps to ensure that this will never happen again by [clarify by some of the following: creating companywide training sessions, installing new back-up systems, creating an internal auditing team, etc.].
Due to this serious oversight, we are going to provide you with [3 months worth of service, or similar compensation, etc.].
We deeply value our relationship with you and are committed to providing you with the highest level of service quality, since we perceive that our customers deserve the very best. If you have any further questions or inquiries regarding this matter, do not hesitate to discuss it with us at [email, phone#, website, etc.].
Yours in service,
[Name of the Company Representative]