For privacy reasons, we are not allowed to cancel a user's active subscriptions, so you will have to do it yourself. Here's how you can do it:
iOS
- Go to AppleID/User-Settings on your iPhone
- Select your name
- Select Subscriptions
- Tap the subscription that you want to manage.
- Tap Cancel Subscription.
You can find detailed instructions on the official Apple Support page.
Android
- Launch the Google Play Store app
- At the top right, tap the profile icon.
- Tap Payment & subscriptions -> Subscriptions.
- Select the subscription you want to cancel.
- Tap Cancel Subscription
For more information, visit the official Google Play Help page.