Moral Dilemma - What would you have done?

New Italian restaurant opened this week, and I went to check it out today. The same family already runs a rather high priced but very, very good restaurant in town, so I quite expected something. Turns out they called it an Osteria and only offer pizze and pasta but I am digressing... When the bill came, they charged me for a much cheaper pizza than the one I had. What to do? Quietly pay that and be a little more generous on the tip, or have them redo the bill in their computer system, which is a PITA? Well, I did the first thing. How long am I going to burn in hell for that?