To cancel a subscription you purchased using Subscribe with Amazon:
Make sure you are logged into the Amazon account connected to the subscription.
Select Manage Subscription next to the subscription you'd like to cancel.
Click the link under Advance Controls to be directed to the main subscription page. From this page, you can end your subscription.
For more information regarding subscriptions billed through Amazon, please visit their customer support center here.
Click here to learn how to cancel subscriptions billed through services other than Amazon.