This happened 2 weeks ago to my friend Helen. She and Clare run a small shop which sells, among other things, high-quality costume jewellry. During one frantically busy period, a lady (in her mid 30s) came in and picked up a necklace and earring set she'd had on lay-by. The final payment was $70.
The next day the lady was back, politely explaining to Helen that when she'd picked up her layby she'd been undercharged.
Pardon? said Helen. UNDERCHARGED?
The customer handed over her payment record, pointing out the addition error that had made the final payment one hundred dollars
less than it should have been. Then she smilingly handed over her card and paid the money.
Helen and Clare were stunned. They are used to customers stealing from them, complaining about the prices and trying to rip them off. A customer politely correcting a mistake which was going to cost her a hundred dollars, a loss they would otherwise have had to eat, is a new experience.
When Helen thanked the woman for her honesty, she replied "I didn't really have a choice. I love this necklace, I don't want to feel like a thief every time I wear it." Yay for good customers!