Rentalcars ripping me off

I booked a car through rental cars for Bidvest. On getting a car I was required to pay separate R5000 deposit. Rental cars had put me on 100 km per day tariff which was going to be costly per kilometers over and above the limit.. Bidvest had other options for me. I canceled Rental cars. Took another option with Bitvest. 350 km per day. At lower deposit. RENTSLCAR is unable to refund me except the insurance portion which I had taken. Now I have paid twice. The dealer and the agent. Online booking has failed me