(I run a credit card through and my register can’t read it. I try a few times to be sure. The customer looks concerned, so I feel compelled to explain.)
Me: “It looks like we’re having some issues reading the card. I’ll just enter the numbers manually.”
Customer: What do you mean?
Me: “Sometimes cards can be demagnetized or worn. We then have to enter their numbers manually.”
Customer: *scoffing* “Well, I know my card works!”
Me: “It may have just been demagnetized, ma’am.”
Customer: “Well of course it was demagnetized! I would make sure it was!”
(The customer remains adamant that her card was demagnetized. She is mistaking the meaning of the word for some sort of card activation. Manually entering the number worked, so I just played along.)