********* and Dishonest about changing a part in my car when I took it in for Service

I am so dissappointed because a month ago I took my car for a major service at Car Care Clinic in Midrand. The Service included changing of Petrol Filter. After dropping off my car, the sales person Hansie told me that they need to do additional work for the car. When I asked him why, he says that the changing of petrol filter - my car uses a different from the one they use, so I they need to purchase a new one. I asked him to discount the service cos the quote he gave included the plastic oil filter that he says cannot fit into the car but it was part of my quote. He then said he will change it because I said I was going to consult legally. Later when I collected the car, he told me he changed the part but he couldn't show me the evidence. He says he recycles the petrol filters and couldn't leave it in the car because it smells. My issue is that he ****. When we got home - the book was not stamped for that part change. I called him and told him. He then said I must bring the car in and I asked my brother to do so because clearly he would rob me again as I dont know anything about cars. I am asking myself as to how many other people is he ***********??