rentalcars.com Avis Belize City Airport pre-payment to rentalcars.com is not fully credited when you pick up the car Belize City belize

I rented through rentalcars.com  They said that pre-payment $538 which I paid was required to hold the car. I subsequenly received an email saying that the rental would be serviced by Avis. when I got to the airport in Belize, Avis had my reservation but said that I had only pre-paid $365 of the rental and that I owed an additional $173.  They also informed me that the car I had reserved was not available and that I would need to pay for an upgrade.  I was stuck at this point because I didn't want to lose my pre-payment so I was forced to pay the upgrade.  All this was not clear at the time of the agreement with rentalcars.com

 Avoid rentalcars.com at all costs.  They are a ripoff!!!!