The majority of the websites that CCBill provides billing for offer "limited access only" with their trial memberships. "Limited" might mean that some or all of the video content on a site is unavailable to trial subscribers. This is done so that users might have a "preview" of the content while still protecting the provider from the risk of someone downloading all the site's files with a download accelerator. In order to gain full access to the site's content you will need to purchase a full membership.
