Defective car and poor service

Bidvest McCarthy VW Constantia Kloof I bought a new polo Tsi the car is giving me problems first it was the window making noise,now is the car having vibrating noise, i took it there they failed to fix it ,now when i call them they dont believe me.the service there is very very poor.The experience left a bad taste in my mouth. im supposed to be enjoying my car but all im doing is keep going back to them to fix it, which they still havent found out what is the problem. im dissatisfied in VW