Unable to attend to supplier non delivery

I went out of my way to rent an automatic vehicle in Argentina. The only site that could provide me with an automatic vehicle was rentalcars.com using OCarrol. The automatic vehicle cost me USD400 more that a manual vehicle. Iwas happy to pay this premium. When collecting the vehicle I got a manual car. On trying to get a refund I was told by Rentalcars.com that they had no control over the supplier (OCarrol) and it was up to them to refund me. I dealt with renatlcars.com and so it was up to them to resolve the problem. Finally I was only refunded 77USD and I had little recourse to recover the difference due to hidden clauses on their conditions. In essence rentalcars.com serves no purpose in the commercial service that they provide. They earn commission purely from managing a website. It is therefore risky dealing with them especially if your encounter a problem with the product rented.