What Kristin said: When I worked in retail sales certain people would buy, for example, a face moistuizertake it home, scoop it out and returrn it with a cheap alternative (drugstore cold cream).
And we gave them their money back.
.....................
When I worked in retail we had a customer who routinely returned a half-dozen pairs of hosiery, saying they didn't wear well. She had been doing this for years, getting 6 pairs free over and over again.
One day we had a new hosiery manager who had been warned about her, and she told her "I'm sorry but it's against the state health laws for us to touch intimate merchandise that's been worn and not washed."
The customer stormed over to the lady's room, dunked the pantyhose in the sink, brought them back dripping on the counter and said "Okay now they're clean. Gimme 6 new pairs".
There will always be customers like that, thankfully few and far between!