faulty vehicle

I bought a Audi a4,2009 model,from market car sales on the 29 September 2015,and the vehicle has been standing since December 2015 till to date and the dealership is not assisting me in repairing the vehicle,I have sent them emails,and they promised to fix the vehicle bt I'm still waiting and this is frustrating me because I am paying for the vehicle that I'm not using,plz assist me,I've lost hope and patience and the manager Albert is very rude