If the payment method for your recurring offer is PayPal, it means Nanacast passed over the recurring billing details on initial subscription.
From then on, PayPal is handling the recurring billing profile and simply reports any billing results to Nanacast via IPN.
For this reason, you MUST login to your PayPal account to cancel, pause, or otherwise modify the recurring billing profile there.
See also:
http://support.nanacast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=92