Customer negative feedback is a challenge to do better and improve more especially if it is related to work operations.

First I would appreciate the feedback and see the pain points highlighted in it. If there's any misunderstanding or grey area, better to make the customer clear on it ask for more concerns. Likewise, if there's any fault from the company end, first apologies and then offer some reward or a pay back to assure customer retention. Then, importantly, take necessary actions on the issue internally and keep following up to ensure problem has been sorted entirely and do some pilot testing anonymously to validate it.

Trying to convince and polite humbelness with customers