Car problem

Hi am Meshack Nsimbini from nelspruit, i just bought a car from Durban aksons viano 250d, I bought the car online and the car was delivered to me after I have signed a contract with them , I didn't get a chance to drive the car or test drive the car, so when the car was delivered I discovered some fault in it , then before the 7 day period I launched a complain to and the seller told me they will replace a car before the deduction was made on 1st of july , now they can't still fix the problem am still not happy with the car, now they want me to pay R200 000 before they change the car, I am now requesting your help.