I had my car detailed at a local hand car wash place (near Manchester, UK) and despite specifically asking for a silver-tier clean, and the owner agreeing that that was what I'd asked for, the guys doing the cleaning started doing extra bits and pieces that looked to me very much like part of the gold tier service. I checked with them while they were doing this, and they reassured me that I was only paying for the silver tier.
At the end, the owner comes over and says "I had the guys do some extras, so you owe me an extra £5".
"No I don't," I replied.
"Come on, mate, help me out here - we looked after you." Was his retort.
Long story short, he and I got into a bit of an argument and I, in the most British move ever, capitulated and paid him his full £20... but the moral victory was mine, or something.
Anyway, I can never go back. And I encourage other people never to go there.