You are mistaken my friend. My intention was not to prove that your car should not rattle. I want to just make a point about the build quality and non rattling nature of Punto. Also rattling is not entirely due to bad quality of plastics. When the car is free from vibrations, rattling will never happens(Thanks to fiat engineers). You ask the service person to sit with you for a drive and show him the problem. I will advise you to show the car to a good alignment shop for balancing and alignment. Good luck.