bad service

hello peter me and my Husband bought a car(hyundai ix35) in march 2015 from Royal Motors krugersdorp then before we bought the car we discovered that the silencer of the car was dead then johan insisted on us taking the car then he will call us to fit on the fitting date i discovered that the part they wanted to install was not correct.wen around buying silencers whereby i ended up going to hyundai and i spent 4400 and sent the invoice through and i havent recived my refund im not happy because the had to give us the in good condition.