To cancel a subscription, on your iPhone go to:
Settings -> Apple ID (Your Name) -> Subscriptions
Find the app or service that you no longer want to subscribe to, tap and select Cancel Subscription. If the button is not there, it is because subscriptions have already been canceled. There will also be a text under the various Plans stating that your current subscription expires: insert date
If you can NOT find that app or service under your subscriptions, then it is because it is not created through the App, and you must contact the company behind the app directly.
How to cancel a subscription from Apple
https://support.apple.com/en-us/HT202039