You can cancel your premium subscription at any time and it will expire at it's next billing cycle.
The simplest way to get to the cancel page is choosing the option in the app
This takes you to our app store page where you can cancel at any time.
Alternatively you can navigate to this via the Google Play app as shown in the following screenshots.
First open the Play store app and then choose the drawer option in the top left.
Then choose "My apps"
Then navigate to Subscriptions and it will be listed, you then select the appropriate subscription.
This takes you to our app store page where you can cancel at any time.