Our free trial is attached to a subscription, so you only need to cancel the subscription in order to cancel the trial.
You can cancel by going into your Apple ID and then manage subscriptions.
Here's more information from Apple on it: https://support.apple.com/en-us/HT202039#subscriptions
Open the Google Play Store and go to Subscriptions.
Here's a helpful article on it: https://support.google.com/googleplay/answer/7018481?co=GENIE.Platform%3DAndroid&hl=en