Dishonest and ********** behaviour

We have rented a quad bike from Europcar Skopelos. Knowing that Europcar is a well known organisation, we decided to go with them. Also dealing a lot of rental agencies we were aware that if we were in accident that we had to pay the excess amount on insurance. Unfortunately this happened. When we went to the agency to sort out everything, they informed us no insurance. Their contract is a small blue paper with no explanation on insurance. Nicolas demanded that we pay all the damages in the amount of 738Euros. He couldn't provide us with a tax invoice as the locals are repairing it. We paid him cash and left with a receipt for only the rental amount reflecting on it. This we saw after being on the ferry back to mainland (as I have sustained serious injuries). This doesnt end year, he also debited my credit card with an extra 900Euros. He cant explain to me over the phone why as he know all of a sudden doesn't undestand English. We have since then enquired at several agencies that the norm us we are liable for the first 350Euros and not the damages. This Nicolas has commit ***** on my credit card and stole from me instead of letting insurance pay.