A butcher accidentally added an extra zero and charged us $640 instead of $64 for our purchase. We realized a few days later when I noticed our credit card spend looks strangely high for the month.
We're regulars so the next time we were there we said "Hey it looks like you overcharged us last week. Can you fix it? We got x,y,z and it doesn't sound like that adds up to $640??"
The butcher people were super apologetic, reviewed their numbers, and refunded us. They specifically said "Wow you're so nice about this! Most people would be shouting and screaming and going crazy"
We're fortunate enough that a hiccup like that isn't a big deal. Plenty of credit card balance to buffer the hiccup and if worst comes to worst, we can issue a chargeback. And if even that doesn't work, eh we'll be unhappy but fine.