They damaged my car instead of fixing it

Book my car for service last week as it was due a guy came and serviced the car after he left I noticed some strange noise I text them they responded that is because they guy found an oil leak on the engine I must book for it to be repaired, I booked yesterday another guy with a lady came to fix the leak after they were done the car is still leaking and the car does not start anymore it showing an error engine failure , contacted them they advised no it’s because they discovered some of the thing that need to be fixed I must pay , but my car was working before they mechanic came now is no longer working it does not start at all