PayPal Accounts:  Log into your account and go to "History" sub-tab of "My Account" tab.
Choose "Subscriptions" from the pull-down "Show" menu and press the "Submit" button.
Select the WebPowerPlus payment, and click on its "Status".  You will be taken to a
Transaction Details page from which you may cancel your automatic payment.  Canceling
your payment immediately stops all future scheduled payments.