Car service city damaged my car badly

So we took our car at car service city in alberton in February because of oil light and loss of power. For two months the car has been there. They made me spend over R20000 worth parts.

Two months later when we picked the car we paid over R12000 labour yet the car was still sitting with same problems plus it was smoking heavily with black smoke which they promised if I drove over 200km the smoke would go of.

Only to find out the car was busy seizing the motor. Now I’m sitting with the car that requires a new engine and they can’t take the blame