I think that's somewhat common with goods and services. Someone will complain, loudly, rudely and repeatedly to get something that is just fine for free.
I work in a grocery store and this happens every day. They try and complain loudly, embarass the clerk, even cursing and making a comotion just to get something free or cheaper. Even just a few cents sometimes. It's really bad because the management tells us one thing (don't give them anything, follow policy) but when they're called to confront the person they give in and act like the clerk was in the wrong. Anything to keep customers, even scammers, unfortunately.
When I cashiered I had a woman try the quick-change bill switch thing, but she was really bad, and whenever she handed me something else to change I'd finish it and shut the til. I think I confused her more than she tried to confuse me.