Over charging on car parts... a mark up of 500%, prices higher then original parts from VW

I took my car to Silverton Radiators pretoria north, the car was making a noise when I drove it, Leonard said he would check & get back to me with a quote. A couple of hours later he called with a quote of R7000 explaining to me that my cars parts are very expensive, and a lot of parts had to b replaced, so me not been a mechanic I trusted him & because I gave my car into Silverton Radiators I didn't doubt a word he said .... not like Silverton Radiators is a backyard mechanic .... I went to pay R3000 deposit... he then said it's the fan belt, tensioner, pully, roller, me not been a mechanic said ok cos he also said he can be trusted. The Thursday paid the balance of the R7000. Then I decided to phone around and get prices for the parts he replaced, keeping in mind it took me 3 days to get an invoice out of him. Went to Goldwagen parts come to R1200, I was disgusted. I then called VW Menlyn the original parts were cheaper then his parts.. VW fan belt R695 his fan belt R995... I went to him yesterday to talk to him and let him explain why he did this & ask for a R5000 refund. He refused to budge, he sat there smug as anything and said "your car drives doesn't it"