Poor service at Hyundai dealership Bedfordview

I recently bought a brand new truck at Hyundai Bedfordview. A week later i asked the deakership to rubberise and open a side door. So i took it back to them, apparently it broke down in the hands of the dealer's driver only to be told that it had a faulty crankshaft I believe this is major mechanical problem. I have asked to be given a new truck and the dealer principal is refusing. I'm grossly disappointed at Hyundai and its poor cars.