A customer moves away from a bank window, counts his change, and then goes back and says to the cashier, "Hey, you gave me the wrong change!"
Cashier: "Sir, you stepped away from the counter. We don't make corrections after you leave. There's nothing I can do about it now. That's the policy of this bank !"
Customer: "Well, okay. just thought you'd like to know you gave me twenty dollars too much. Bye."