Subscriptions will renew automatically unless the option to auto-renew them is turned off at least 24-hours before the end of the current period. Payment will be charged to your iTunes account at confirmation of purchase. Your account will be charged for renewal within 24-hours prior to the end of the current period.
Subscriptions can be managed and the automatic renewal feature can be turned off in your App Store account settings after purchase.
For a step-by-step guide on how to cancel your subscription, please check this link on the Apple website:
Your subscription will renew automatically unless you cancel prior to the end of the month. Subscriptions can be managed from the My Subscriptions screen in the Play Store app.
For exact steps on cancelling a Subscription from your mobile, please read the aricle on the Google Support Page:
You can also cancel your subscription via your desktop/notebook/browser. The steps to follow are listed here: