I worked as a customer services supervisor among other things while I was a student. I’ve never been yelled at so much in my life. Most of it was because of their own stupidity. The rest of it was due to ridiculously inconsequential stuff that I wouldn’t have batted an eyelid at. I only ever got slightly annoyed once when a woman shouted, “You don’t know what you’re doing!” because she’d forgotten her purse and I wasn’t going to let her take a trolley-full of shopping out the door for free.