If there is a problem and the client complains about it, you should quickly answer the complaint and try to solve the clients problem. You also need to follow up and improve your business processes to rectify the problem.
Listen to the complaint and sympathise with the client. Show empathy towards them.
Try to solve the problem or situation as best as you can. If you cannot refer them to someone who can
Make sure the client is completely satisfied; you may want to provide some special service or a reduced price on another product. This is to assure the client will come back for more business.
Try to rectify the problem. It is in your best interest to try solve any problems and try to make sure that they don't happen again. It is foolish for a company not to use clients complaints to initiate a corrective action.
Satisfaction Make sure by the end of it the client leaves satisfied. Him/her have been heard. Dealing with a customer complaint can lead to a more loyal customer than others who may not complain or have problems.