You can change or cancel your subscription by clicking here or visiting the Play Store and searching for the Warner Archive app. You'll see the option to cancel if you have a recurring subscription.
If you signed up via Google Play through the Warner Archive Android app, you can cancel your subscription by visiting your Google Wallet and following these steps:
Go to wallet.google.com and sign in to your account.
On the "Transactions" page, find and click on the subscription you'd like to cancel.
Click on Update or cancel your subscription.
Click the Cancel subscription button.
Please note: Uninstalling the Warner Archive app will not automatically stop your subscription. You must cancel your subscription to end your subscription. If you uninstall the app without canceling your subscription, you will still be charged.