Have you actually read what has been printed onto the invoice they supplied you with. They will often slip in a 'wheel allignment', 'wheel balancing', 'fuel system clean', 'windscreen washer additive', new windscreen wiper rubbers etc. There are heaps of services and components that they may try and on-sell. Many people don't have a clue and just pay up. I always provide the Service Advisor with a printed list of what is to be done with the comment 'no additional work or replacement of components (other than required in service) will be paid for without express permission of owner (I'm usually the one who sits patiently in your waiting room, drinking your coffee, eating your biscuits and watching your Foxtel).