faulty vehicle

I bought Audi a4 from market car sales and the vehicle broke down in December and now it's been three months requesting assistance from the manager Albert Lottering without any luck,the manager is so rude and full of empty promises,they promised me that they Wil heel fix or repair the vehicle but nothing has happened and I'm paying the bank for a vehicle that I'm not using and at the end of March it will mark 4 months,I am highly disappointed with the treatment I received as a customer from market car sales and I'm still without a vehicle because of them and they have done nothing to assist me to fix the vehicle.On the 23February 2016 Albert told me to write a letter that I will not take them to ombudsmen or media because they gonna give me 15000 to help me fix the vehicle and after I wrote the letter he told me I will not get the money immediately I Wil only get it on Monday 29 2016 latest and till to date I haven't received any money from the dealership and I haven't heard anything from them.Please assist me to get refund and I want to cancel the deal with immediate effect and I dnt ever want to deal with market car sales and I will never advise anyone to purchase a vehicle fro