Failing to rectify their poor work

On 21 March 2015 I took my Isuzu KB300LX for shocks and rear leaking bearings. They replaced the shocks same day and told to come back Monday for the leaking bearings as they had ordered the wrong parts. On Monday 23/03/2015 they replaced the bearings and seals and charged me R3 380. Two weeks later the bearing seals were leaking again and I took the car back and they undertook to replace the seals again which they did on or about 7 April 2015. A week later on 13 April 2015 the bearings started to make an irritating sound and I took it back to which they said lets change rear tyres as they can cause the noise. Today 20 May 2015 the bearings are leaking again and I took the car back and requested that they refund me my money so I can take the car to General Motors (GM) as I gave them 4 chances already and they failed. They refused to help me and the manager screamed at me. I am now stuck with a car that has leaking bearing seals and oil messed up tyres and have to pay another R5 000 to get the car fixed by GM as these Tyre Mart people have proved that they are incapable (failed 4 times already) and they do not want to refund my money after failing to deliver.