How to cancel active subscriptions purchased on the Play Store (Android)
On your Android device, go to subscriptions in Google Play.
Select the subscription you want to cancel.
Tap Cancel subscription.
Follow the instructions.
Tutorial here: https://support.google.com/googleplay/answer/7018481?hl=en&co=GENIE.Platform%3DAndroid
How to cancel active subscriptions purchased on the App Store (iOS)
Open the Settings app.
Tap your name.
Tap Subscriptions.
Tap the subscription.
Tap Cancel Subscription. You might need to scroll down to find the Cancel Subscription button.
Tutorial here: https://support.apple.com/en-us/118428
Resources:
Refund policy here