audi rs7 faulty brand passing the buck

2014 when i bought my audi rs7 it had rattles on the dashboard from the speaker, the heads up display and the gearbox gear change are not smooth also hear a knocking effect when engaging between gears, this car was fixed at audi arcadia for a number of times without luck i moved to audi menlyn they did not help but realised after that they were of the same mccarthy group, with frustration i went to audi hatfield their reception is good they attending to my car but they tell me they won't touch the gearbox because i had aftermarket rims fitted in my car. but i am asking myself why audi arcardia kept replacing parts on my car when the knew i had after market rims on that car ??? double standards