It turned out to be Europcar. There were cheaper options with other small rental companies, but I chose a big brand to avoid hidden fees. However, it was the same! At the counter, I explicitly told them I didn't need insurance as I had purchased it domestically. The representative smiled and agreed. Later, she said she upgraded our car for free but never mentioned we would be charged for it. In the end, we received a bill for thousands, including upgrade and insurance fees!