You need not be discouraged if the customer gives a poor feedback about your product or service. The very fact that a customer has bothered to give a feedback is itself a great opportunity. Most customers don’t bother to give feedback. Instead they choose never to deal with that service provider again. In your case, if you have been given a feedback, it means that customer is giving you an opportunity to correct your service deficiencies and offer him the service again. But do not be late. Be prompt in calling the customer to thank him/her for the feedback and also let him know that you care. Make corrections to the service and make sure you inform him. Pls invite him to utilise the service again.