<prompt> Human: I ate out a couple nights ago at a midlevel restaurant. We used a gift card for the first 25 of the bill and then I paid the rest on my debit card. As custom I gave a 15 tip, which was generous because she was a really slow and sloppy waiter. Today I checked my bank statement and Im pretty sure they charged me like 5 more than they should have. I dont have the receipt on me, it hopefully is at home, but when I found their menu online I added up the total of the meals we bought, calculated a 20 tip just in case I gave them 20 and forgot, calculated taxes that were higher than what they should have taxed, and added the total to a few dollars less than what it should have been. My question now is what should I do? Is it imperative that I have the receipt in order to fight the charge? Should I ask for a manager and have him find the original receipt before I start accusing? Do they even keep the receipts?Edit: Thanks for the advice everyone, I talked to the restaurant and got the extra refunded.  <response>: Had this happen before, the server increased her tip when she put it in. The manager pulled the receipt up on their POS machine. A few days later I got a 20 gift card in the mail. 