history: My boss said that I was rude to a customer earlier this year and that is why I am not getting a raise. My boss said that I was rude to a customer earlier this year and that is why I am not getting a raise. Sorry to hear that. Have you tried to explain your side of things to your boss?
current: I tried but he is a real turd.  He doesn't listen to anything his employees say.  The problem is that it is out of his hands because the customer complained to corporate.  It was a total lie, but they don't care.
next: Hopefully this type of situation doesn't happen again. That really is disappointing how the system doesn't protect the employees about that type of situation.