I hired a car from budget SFO on Christmas Day, and returned it on New Year's Eve. All within the times on my booking.

The final charge was about 600 $ over the email confirmation.

Turns out that when I picked up the vehicle, the counter agent added on a load of extra, and unwanted insurance options. He never asked me. However, following an 11 hour flight and being jet lagged, I unwittingly signed the agreement without looking into it in much details, assuming, albeit incorrectly, that items wouldn't be added to my bill as budget is a well known and trusted firm.

Any recourse?