I once had a line of two customers when I was a cashier, and the first one was paying in dimes and quarters. Not a huge order, just $2.15.
Queue the second customer. She walks up and asks aggressively “Are you new here?”
I reply, taken aback “No ma'am. I’ve been here for about two years.”
“I thought you would have been faster by now,” she snaps back.
Well, I was already having an off-day, so I decided to get a little petty. She slides her card, and immediately I hit ‘Cancel’ on my register. She tries again. I hit 'Cancel’ again. Slide. Cancel. Slide. Cancel.
By the fifth time, she’s turning her card over in her hand and asking “What the HELL is wrong with my card??”
I reach over, taking it from her hand and ask “Have you had this card a long time, ma'am?”
I slide the card through without any problem (obviously), and hand it back politely. “I thought you would have known how to slide it by now.”
Her face sunk, probably realizing but probably not. She left, and I proceeded to tell my manager out of guilt in case the woman complained, and my manager high-fives me but then tells me to NEVER do that again.