Sixt Charged Me €176 for Insurance I Declined

Although I paid for coverage, the staff tried to sell me additional insurance, which I declined. He warned me that I would be driving without insurance, so I used the car for 5 days in fear. Despite this, Sixt charged me an extra €176 after I took the car and left the airport. When I asked the same staff member about this amount, he said he didn’t understand it either but promised to look into it. After returning home, I emailed the company and requested a refund, but they replied, saying the amount was for insurance. Charging money without asking, telling me I was driving without insurance, and taking money after I had already left the airport—this is shocking, and I feel they extorted my money.