double downgrading after taking over the contract

Hello, I have a serious problem. I had a cyclist lightly hit last year. At that time the insurance contract ran on my mother with SF15 and I was registered as a holder. My mother was reclassified to the SF6. Since 2000 I have had my driver’s license this would correspond to the SF6 (if there had been a contract in 2000) So I took over the vestrag with SF6 which was confirmed to me by the broker. Now, however, the new insurance has me in the SF3 (i.e. from SF6 in SF3) is set on the grounds that a damage has been regulated last year. Is that correct now? For my feeling a double downgrading has been made here? I can buy back the damage for 300 Eur until December. Can I withdraw from the acceptance of the contract? Thank you for your help. With friendly greeting Pepe