Bad services and sales

I will like to show my disapproval of Renault Sales and Services. I bought a new Renault Duster 4x4 to tow my camping trailer and they informed me that I can't fit any other tow bar other than their own because it will void the warranty. So I agree that they can fit the tow bar at an extremely expensive cost. Just to go on holiday and find that the tow bar is not up to standard. Firstly the tow bar bent to the right, secondly the tow bar has to much play which causes it to lower and my trailer jockey wheel was hitting the road. I then had to put on a riser plat to lift the tow bar.

After reporting the problem to Renault Northcliff they came back to me saying Renault SA has void the warranty on the tow bar because of the riser plat as no permissions were requested for it to be added. My argument is that is that non of this was explained to me by the sales agent when I requested for the tow bar so how can the warranty be void if non of this information was relaid to me. If I knew that the tow bar was not going to work for towing of my trailer I will have never bought the vehicle.

I have requested refund on the tow bar and its just being refused.