Monthly charges for a non-recurring subscription.

Like the title says. I purchased a non-recurring subscription. Yet the system tried to charge my card thins month again; but it got rejected due to lack of funds on that account. I can't cancel it from the website since it's non-recurring. I tried to remove my billing info from the website, but apparently there is none to remove, yet a charge was attempted. What do I do? I DO NOT want to pay for another month, as I no longer have time to play anymore.