Extra products in your Bill and Service Charge
This sometimes happens in places where the service fee is charged. You ask your bill and you notice there couple extra beers that you don't order. You ask the waiter to fix the situation and he apologizes and says that the beers are from other table and then he back with a new bill. The problem is the sometimes they remove the beers but keep the service fee (percentage) applied on the old value. So always pay attention if you are paying what you should.