You can cancel your plan by clicking the Profile button in the top right corner of the screen, then clicking ‘Profile & Subscriptions’, then clicking ‘Manage Plan’:

Note: you can only manage change your subscription on the platform on which you originally bought it. That means if you bought your subscription while using Hypernatural on a web browser (such as Chrome or Safari), you'll need to update it on a web browser. If you bought your subscription in a mobile app (i.e. from the Google Play Store), you'll need to update your subscription in the mobile app.

Your subscription will carry over between web browser and mobile apps--you'll just need to log in with the same email.