HUK Coburg does not take into account public service !

Hello together, I have been working in the public service (energy supply) since 01.07.2013. My car and motorcycle are both insured with the HUK. Now I have sent the certificate (public service) of my employer to the HUK where I demand a recalculation and correction of my insurance contributions from 01.07.2013. Below the answer of the HUK: Thank you for the explanation. We can document a contract with the HUK from 01.07.2013. Unfortunately, the conversion of your contract to the latest tariff does not result in any savings for you as a whole. We therefore recommend you to continue your contract unchanged. In the event of a future change of tariff your activity will be taken into account in the open service. What should I think about it? My insurance man told me that 20% savings are included when you are employed in the open service. Thank you and greetings