I suspect that buried somewhere in the terms of service they had you click "I Agree" on, there is probably something about automatic renewal at that rate. Ask them for a copy of what you agreed to and read through it carefully. If it's in there, you're almost certainly out of luck. It's devious, but it's legal.
Another problem is that the law may treat the past six months of payment as having been done with your consent--those charges would have appeared on your credit card statement, and it's your responsibility as a consumer to review your bill and challenge anything you don't approve of. If you paid it without complaining, then it will be difficult if not impossible to undo that.
If their terms of service say nothing about the charge, then it's worth consult an attorney directly.
Answered on Mar 03rd, 2016 at 8:05 AM