Angry customers are bound to come your way at sometime, help to make the experience better for both you and the customer by knowing how to act in such a situation. A few things that you will need to do are apologize for the situation, try not to become emotional yourself as this will only make matters worse. Be diplomatic, show the customer that you understand their problem and also thank the customer for their feedback. The aim in all you do is to show the customer a lot of kindness. This is a response they are not expecting and so instead of continuing their ranting, it is highly likely that they will calm down. Once they are calm you can bring resolution to their problems.