Unsatisfactory Car Service.

I took my BMW 328i for service at 127k milage on the 16th of November 2017, The service attendant diagnosed the car and contacted me to say except for the spark plugs which was said will be changed at an amount of R6k, they discovered other serious things which will amount to +_14000 , I consented them to continue with the service. My problem is,upon collection of the car after service, it started giving me problems which it never had before. It was failing to breek sometimes, losing power, sluggish,constantly showing drive train caution and smelling fumes of oil from the engine. Making noise from the engine, discharging black smoke, jerking off and misfiring. The right tyre from the drivers seat making noise and imbalance movement s. My main problem is: The service attendant contacted me to say my bill has increased worse from the initial bill due to serious damages discovered from the car. I did not understand why a new bill or being charged again for the damages that were caused by their technician. My car was never acting up before service and normally, after a service it is expected that a car show perform well than before. I am shocked and need your help and advise in this regard as BMW seem to take this for granted.