To cancel your recurring payment, click the "Recurring Payment" link or navigate to Products > Billing History [http://www.filefactory.com/account/services/billing.php].
You will see a list of current recurring payments if you have any. Just click the 'Cancel' link to stop a rebill from occurring again.
You will still be able to use your Premium account until it expires, but you will not be charged again.
Note: if there is no Cancel link, it means that either your recurring billing has already been cancelled, or that your account does not automatically renew, so no further action needs to be taken.