At dinner with my hosts in an Italian restaurant, the service was chaotic: my starter and main course were delivered at the same time; other main courses came 20 minutes later so I had to have mine reheated; the white wine was at room temperature; the pizza of one of my companions was lots of puffy bread and not much else; the waiter presented our bill with a cheery "whenever you guys are ready" despite my having asked him earlier to hold it for me so that I could go discreetly to the desk to pay.
All this was not a disaster, but slightly annoying. I made my point to the manager who apologised and offered me a discount, which I gratefully accepted as reasonable amends. I asked her to add 15% to my credit card as a tip to show my appreciation of the gesture and that there were no hard feelings.
An hour later I got a text message from my credit card company showing the amount billed. They had added 30%.
When I went back the next day, another manager handled my complaint. I demanded a refund of the double tip, not just the excess. He didn't argue.
He handed me the cash with a smile and instructed me to "have a nice day!"