The way I handle difficult customer interactions is one good thing I learned about customer service, doing that for a few years plus growing up with five sisters, is let them then listen, but listen really close because chances are it's not you that they're mad at, it's a policy, it's something they didn't understand, it's an item, it's something you can probably find a way to resolve. Let them print it out, take notes, let them know that you're really listening to them explain, I understand this is upsetting, and then ask how you can work with them to resolve it and see what you can do to resolve their issue. There normally is a way to solve an issue. Most times, the best thing you can do for someone that's really upset is listen and acknowledge them and let them know, I get you're upset, I'd be upset too if this happened to me, and just kind of connect with them and see if you can work out their problem.