Very uncertisfied customer

I took my car for a major service yesterday. I knew it had a problem with gearbox. The person who was helping me, I asked what specifically they do on vehicle check. He told me that the plug in the diagnostic machine meaning all the faults will be detected if any. So to my surprise later that afternoon when I get there to collect the car, when I ask about any faults he said there was none. I really believe that they charged for something they didn't do. I also asked for a car wash. The hand prints that were left by my 2 year old son on Monday they were still there on the bonnet even on driver's side windscreen the fingertips were still showing. I'm very disappointed with the service I got there