To close a Channel, you'll first need to login to BigMarker. Then go to your personal account settings located under your profile, and click Settings. Then click Close Account. Here you can choose to Close Channel or Assign a new Administrator. If you choose Close Channel you will be directed to the Billing Page of the Channel you wish to close.
Once you delete the Channel, it nor it's subscriber information can be retrieved later. As a result, you may want to downgrade the Channel to use at a later date.