Refund for monies paid to Toyota Secunda on misdiagnosed car

On the 7th of March 2018 (Wednesday) my car had an engine light on the dashboard. I towed it to Toyota in Secunda. They diagnosed that was the turbo that was faulty and needed to be replaced. I paid them in full (R21000) for the replacement of the turbo and they promised to have the car finished on that week Friday. There was no communication on Thursday. I called them on Friday for status of the vehicle. They claim a wrong part was delivered and they will have the new part on Monday. Monday they informed me that the part was not delivered from Johannesburg. Tuesday Morning (13 March 2018) decided to tow my car to Toyota Springs. Toyota Secunda had stripped the car and they did not issue all the parts of the car. When I query for the parts they removed in the car they claim that they had misplace them. They finally delivered all the part to the Toyota Spring on the 15 March 2018. Toyota Springs replaced the Turbo with a new turbo and the initial problem was not resolved. After some investigating they diagnosed a motor being faulty (which costed me R2500 to replace) not the turbo that Toyota Secunda Diagnosed. Toyota Secunda now refuses to refund me as they had wrongly diagnosed the car.