To cancel your subscription on your iPhone:
1. Go to Settings > [your name] > iTunes & App Store.
2. Tap your Apple ID at the top of the screen.
3. Tap View Apple ID. You might need to authenticate your Apple ID.
4. Tap Subscriptions.
5. Tap the subscription that you want to manage.
6. Tap Cancel Subscription to cancel your subscription
For more details please visit Apple Support page https://support.apple.com/en-us/HT202039