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." "If you don’t cancel more than 24 hours before your renewal date, your subscription might renew."
Is auto-renewal already off? Does it say it will renew on a certain date or does it only say the subscription will end then? If you are not seeing an option to cancel then it probably means the automatic renewal has already been turned off and the current subscription is simply waiting to expire.
iTunes [Store] Support - Use this form for assistance with account and billing, code redemption, or purchase questions - https://www.apple.com/emea/support/itunes/contact.html
Perhaps:
iTunes Store: About In-App Purchases - http://support.apple.com/HT202023
If you don’t see your in-app purchases - https://support.apple.com/HT204530