Terrible repairs with bad service

We bought a Demo vehicle at Volkswagen Centurion - So it is actually a new car- in June 2014. December in Jeffreysbay the car broke down and we took our vehicle to Dirk ellis motors in Jeffreys, they said it was the gearbox, after 3 weeks in repairs we picked up the vehicle in Tzaneen January. A week after we picked it up the car broke down again, so the vehicle is still not fixed. We went to lani Motors in Tzaneen the manager Paul and the Mechanic Wayne told us the vehicle is fine. Volkwagen is moving the vehicle every where and still don't repair our vehicle after we are paying loyaly on the installments every month. I think they must replace our car until they found new mechanics proper mechanics who know what to do on a vehicle and who doesn't depend on a computer for repairs. Why must I still pay for a vehicle that is still not in working condition. I won't ever recommend this Pathetic dealership called Volkswagen to anyone. Not for Buying or repairing they are useless, and thats me being nice.