How Do I Cancel My Account?
You can cancel your Account (deleting all Podcasts and associated data) at any time by going to the Account link at the top of your Dashboard, clicking Close Account in the lefthand sidebar, and follow the instructions listed on that page.
This will delete all of your Podcasts and their associated data. If you want to just delete a single podcast and not your account as a whole please see the article about Deleting Your Podcast.
If you are still in your trial period, your credit card will not be charged. Only the account holder can can delete the entire account including all podcasts, Collaborators cannot.