Log into your Podbean account, go to "My Dashboard" in the top right drop down menu. Then, click "Premium Content" on the left sidebar.
You can listen/view the premium podcasts you’re subscribed to here. Click on "Info" to see the detailed information about a subscription. There you can click the "Cancel Subscription" link.
If you have any questions or are unable to cancel the subscription, you may click the "Contact Publisher" button to email the podcaster for help. The podcasters are able to manage the subscriptions in their Stripe/PayPal accounts.