I'll handle a difficult customer interaction by first understanding what the issue is. Everyone always has a reason to be mad and step one is to figure out what it is. After that, I will keep a level tone and discuss the options to resolve the issue and see what I can do for them and what I can't and try to understand the situation in the whole and then come up with a solution whether that's bringing in a higher manager or giving them what I can or offering this or that to where the situation can be resolved.