Tow Pro: Changing Weights On VIN Plate

Hi Phil . Can you help me with a weight increase on a VIN plate please , My caravan is registered at an ATM of 3000kg but the axles are rated at 3200kg and the tyres are rated at 4500kg combined ( i have a two axle caravan ) , i would like to increase my ATM to the 3200kg weight but the company that made the van is the only one that can issue a new VIN plate and they wont do it for me , is there a reason why they wont go to the maxamin or do they leave a reserve of 200kg for safety reasons , if not can i force them to increase the ATM ? Kind Regards Martin