If you have a business, and your customers love you, it’s almost certain that their is someone who does not love you. That’s why even businesses that have a ton of excellent reviews, will once in a while be hit with a bad review from a customer. If it happens to you, don’t panic, such is life. Might as well deal with it. The first thing you must do is learn, and the respond. Try to fix the problem. Try to make that client happy. If you can’t, then just learn from this, and keep doing better each day.