IF THE REVIEW IS MOSTLY FAIR:
  "Thank you for telling us — I'm sorry we let you down. You're right that
  [the true thing]. We've [what you changed] so it won't happen again. I'd
  like to make the rest right — please call me directly at [number]. — [name], owner"

IF THE REVIEW IS MOSTLY UNFAIR:
  "Thank you for the feedback. I see this differently, but I won't argue it
  in public. [Own the one true sliver, if there is one.] I'd like to understand
  and make it right — please call me directly at [number]. — [name], owner"