If's its a brokers you should have received their " Terms of Business" Letter. This should contain the fact that they charge an admin fee of €25.00. Brokers receive commission of 5% on motor policys and the fact your premium reduced by your change in vehicle means your broker had to refund some of the commission to the insurance company that was already paid to him by the Ins Co when you took out the policy.
Do you expect the insurance broker to inform your insurance company of your change of vehicle, return your old insurance certificate, obtain your new certificate, post your new certificate to you, and all for a loss?