Reminder for alleged lack of insurance

Hello together! I have a problem with Strassenverkehrsamt. Had had me an offer of an insurance about automobile Vers.. But did not accept this and was and am still with my old verse. What I did not know is that the verse, where I asked for me at the registration office probably signed off (display according to § 25 Ab.s1 FZV) and I was therefore considered uninsured, although I was still with my old verse.. After I was written, I have this by mail and Tel. explained and my present verse. wrote a confirmation to the street prison. I thought that this would be settled. But now came a warning, the office continues to demand the money. Do I have to pay? What should I do? Thanks for the help!!