BMW please return my car

I took my car to BMW East London for diagnosis and repairs. It was displaying a "drivetrain" message on the dash screen. They diagnosed that it has a timing chain problem. They gave a quote of around R25000 and I gave a go ahead for them to do the repairs.

Weeks passed with no contact from them I had to do a running around trying to get what is happening with my car. Eventually I was made to speak to a technician who told me that when they were testing the car after fixing the timing chain they discovered that they drove the car without oil. I questioned if this did not damage the engine, he said no, I raised this with the manager and he also said he is sure the engine was not damaged.

After a few weeks when I was demandin that they return my car, they gave me a new quotation of R196000 telling me that I need to buy a new engine. They refuse to take any responsibility for the damaged engine which by their own admission they drove my car without oil. My car was driveable when I took it to them. Now it is no longer driveable.