The following procedure describes how to manage Subscriptions that are active against your Apple ID.
First open Settings (the grey gears icon) and then scroll down the left hand column and tap upon iTunes & AppStore. This will display your Apple ID which is your email address associated with your Apple account.
Tap upon your Apple ID; then tap upon View Apple ID. You will be asked to enter your Apple ID password.
This will display your Apple ID Account where you can manage the Credit Card against your account, Alerts and Subscription. Tap upon the Subscriptions button.
This will then display a list of all your Subscriptions. Tap upon the Subscription that you would like to change.
By default the subscription will be enabled for renewal as shown below:
Tap the On button to change to Non-Renewable.
This has now disabled renewal of this subscription. Tap the Done to close the Apple ID Subscription management dialogue box.