Since the purchases of our monthly/yearly membership subscriptions are processed through the App/Google Play Store, you will need to head into your iTunes or Google account settings to manage your active subscriptions.
This can be accessed from the "iTunes & App Store" section of your iPhone settings, but you can find detailed instructions on how to cancel your subscriptions through this link: https://support.apple.com/en-us/HT202039.
Go to payments.google.com. Located along the left side of your screen, select Bills and accounts. Select the subscription you want to cancel and tap Cancel subscription.