Is this a legal matter Guerin car rental scam?

I started to conversation with “Hi I have a reservation” the guy at the counter then said with a condescending tone “congratulations”. And then the whole process went downhill. Not sure if it was because I was from North America, a woman, or because the reservation was through National. I have executive elite status with national and a professional for work. My company has a contract with National and they cover the insurance. The counter then proceeded to try inform me that for 300 euros more than agreed contract I would not be charged 3000 euros on two credit cards and forced to pay up front 31,000 in case anything happens to the car. I started to get annoyed knowing exactly that he was scamming me. He spoke Portuguese to his colleagues thinking I couldn’t understand his derogatory comments about me. I then left and went next door to Europcar, spoke to their manager and they informed me that what Guerin was doing was illegal. They were aware that Guerin does this for North Americans/ others on a regular basis. They gave me a equivalent car at 30 euros cheaper and included the toll fees. No extra deposits other than the regular rental amount. One credit card. Never go to Guerin...I was warned about the one downtown but I never had issues elsewhere in Europe. Is this just this company or are they breaking the law like Europcar mentioned? I have also made a formal complaint with National.