Europcar Mexico Rip off on insurance! San Jose del Cabo Mexico

I rented a car on expedia through Europcar Mexico. Prices were great! When I got there to pick up the car, they woud not accept that I have premium insurance from American Express. I even got the Amex agent on the phone with them to verify them that I have full coverage already! They wanted to see a letter from Amex! This is nowhere mentioned on expedia. So those "great" prices suddenly quadrupled. I asked them if I would be refunded part of the insurance money back if I manage to get a letter from Amex. They said yes, I can email them the letter and I will not be charged insurance for the days after the letter is received. WRONG! They charged me for the whole rental period even though I emailed them the Amex coverage letter. They never replied to my email and the follow up email. They are sneaky. They say things that don't match each other. Never ever rent a car from this company!