My apologies for the delay in getting back to your enquiry message that you sent on [DATE].
We, at [COMPANY NAME] treat customer enquiries with the utmost priority and certainly not this way. I assure you that this was a one-off incident which is definitely not in-line with our company values and policies. We promise to do better than this, henceforth.
Now, coming to your query: [ANSWER CUSTOMER QUERY]
If you have any further questions, please reply to this email and I will get back to you right away!