Unacceptable service

A vehicle was taken in to Bmw for a knocking sound. The car is still on motor plan. When Bmw stripped it they found a different ***** and apparently something called a spacer. Now they saying this should not be there and not willing to pay for the repairs. How is this fair? If the dealership sold the car like that, how is it fair to the client? Someone should take responsibility here between BMW SA and the dealership. We have tried speaking to the dealership and logged a complaint with customer care but no help has been received so far. I think the dealership should then take their car back and refund this every cent that was paid for the past few months since it was purchased! I always applauded BMW for their great service but this is unacceptable to say the least!