Insurance has been canceled, and now?

Hello, My friend and I bought us a pass on 29.03.2018 and were still admitted on the same day. My friend, vehicle owner, of course, had the EVB number given to us via an online insurance (via Check24). On 10.04. we received the documents. On 19.04. the insurance sum of 152.46 € was collected… On the same day we were deducted 1.50€ for a supposedly justified rejection… On the same day the amount was written back to us. communication only possible via e-mail… How should/can we proceed? Search for new insurance – clear, but then? Do we have to go to the registration office or can we do it automatically?