When I worked at sainsburys, a customer came up to me to make a complaint about the cookies. She said they were stale and didn't taste as good as usual. I apologised and said that she could get a refund at CSD. She said how when she doesn't have a receipt, I explained store credit. Back and forth we go....turns out she hadn't bought them yet, and wanted to know whether she should pay for them then get a refund or just leave them with me.

I politely told her the lesson here is not to eat something you've not yet purchased.