To cancel your free trial, simply cancel your subscription.
iOS
Cancel through your Apple ID by selecting Manage Subscriptions.
For more details, visit Apple’s page: https://support.apple.com/en-us/HT202039#subscriptions
Android
Open the Google Play Store and navigate to Subscriptions.
Check out this helpful article: https://support.google.com/googleplay/answer/7018481?co=GENIE.Platform%3DAndroid&hl=en