Virseker debit order

I requested a quotation from Virseker, Dec 2024, not accepting the quotation, VERY BAD. I insured at a different supplier. I made it clear via mail, webpage and phone calls to Virseker, THAT I WILL NOT BE INSURING WITH THEM. Now 9 months later they are still deducting every month from my bank account. Every month I have to stop the debit order at my bank, every month I have penalty fees, because someone is not doing their job. It puts me in a bad light with my credit profile. Been to my bank, they can stop this debit order. HOW DO I STOP THIS DEDUCTION?