I ran into this with several other websites also. I've had my account debited for stuff I did not agree to.
I called them with the threat of reporting them for, a theft by deception, for not 'clearly' stating it and 'providing an opt out button'. Got all my money back in nano seconds. They DO KNOW that this is deceptive and illegal practice.
This is a practice that really should be reported each and every time by users when it happens but most people rarely do.
BTW: talk to your state park in person. You will find out that you DO NOT 'have' to use reserve america at many of them. Also the CG's that state you have to use Reserve America? Same thing. You CAN make reservations directly. They all just hope you use RA to reduce the phone calls. :W
I refuse to use Reserve America.