That is unless you get something wrong. And then, hopefully they will let you know. Some will quietly leave of course so you need to keep your eyes open and track your customer regency (how often they patronise your?business).
Mistakes happen. And when they do, they are a golden opportunity for you to do two very important things.
Firstly, you can look at why things went wrong. Were your team following procedures or was there not one there to follow. The minute you rely on a person using their common sense you are screwed I’m afraid.
Fix the problem and then ensure it doesn’t happen again.
Second. You don’t want to put the customer back to where they would have been before the mistake happened. You want to put them in a better position. The number one best customers are the ones who were once upset but you brought them back round.
Give them a freebie. Throw in some goodies. Give them something of high value. After all, they just took the time and trouble to help you improve your business. They could just have easily have left you and told all their friends, family and Facebook community.