"One time, there was a woman who was complaining that she didn't get her order yet and that she had been waiting for 40 minutes. She was really yelling at the top of her lungs, which naturally stressed me and my staff out. I stayed calm though and reminded myself that nobody should have to wait that long and that I wouldn't want my mother waiting that long.
I apologized to her and asked her what the problem was. I acknowledged that it should never have happened, and then I gave her what she needed. On top of that, I gave her a credit on her next order, that way she'll be encouraged to come back and give us another chance to give her good service."