View, change, or cancel your subscriptions - https://support.apple.com/HT202039 - "Learn how to view your subscriptions that renew automatically, change your subscription period, and turn off Automatic Renewal." "Your membership or subscription might renew if you don't cancel your membership or subscription more than 24 hours before your renewal date."
Jan 2017 - https://discussions.apple.com/thread/4190854 - cancel Hulu subscription that wouldn't appear on iTunes Store site