My only customer service experience is working at as a waitress at a full service restaurant my parents used to own. I once had a lady go nuts because I gave her a "cup" of soup which is what she ordered, but she thought it was a bowl. Our "cups" were just smaller bowls. I told her that it was a cup and she still went to talk to the manager, my dad.

Also I hated serving bus loads of people that would come in, no one seemed to understand that someone was going to be the last one to get their food. Rocket science I know.