Driving performance exceeded – still well gone?

Moin together. My father has always insured his car with the HUK and stated 12000 km of driving power at the time of the application. The last one was a rempler and due to the damage signs we also had to indicate the KM stand and it came out that we had exceeded the annual driving power of 12000 km far. On average 28000 km came out. My father used to drive more than today. If today still 10000 km come together this is already a lot. We have now received an additional supplement on the change in driving performance. They have chosen Class 4 (20 – 30000 km). This results in an additional contribution of 100 € per year. Are we still able to get away with this? If we were to reduce the driving performance again next year as they are currently also we would have paid only 100 Euro more. Or should we contradict the supplement on the grounds that the multi-speed services corresponded to the first years and since then only few r than 12000 km a year? Could the insurance still ask for a contribution?