Subject: We’re sorry about the bad customer support experience.
Please accept my sincere apologies on behalf of our company [COMPANY_NAME] for the negative experience you had due to one of our customer support agents.
This is certainly not the kind of experience we want our customers to have and we promise to do better in the future. We’ve also assigned our top support agent to your case, and he will take it all the way to its successful resolution.
We’d also like to inform you that the support agent you had to deal with has been sent for retraining and evaluation.
I thank you for your continued patience and apologize again for the inconvenience.
If you have any further questions, please do not hesitate to contact me.