I've had multiple positions in my lifetime where I had to deal with customers on a daily basis. Those who are irate, impatient and often rude can only be dealt with one way. With kindness. Firstly, LISTEN to their problem. Void the outside noises and really get a grip on what they are complaining about. Second, APOLOGIZE for the inconvenience. Next, SOLVE the problem (if you can!). If you cannot solve the problem, be sure to remember all the details and bring it to management or discuss it with one of your co-workers. Lastly, THANK them for bringing the situation to light. They will get the idea that you really do care about them and want to avoid it again. So to break it down: LISTEN > APOLOGIZE > SOLVE > THANK or simply put, LAST. It helps me out immensely when this occurs, and also, its a perfect way to answer this question when it's brought up in an interview. Hope this helps!