Manage and Update your Apps: http://support.google.com/googleplay/bin/topic.py?hl=en&topic=1046717&parent=1100168&ctx=topic
You can easily see all your subscriptions on your device:
Here, you’ll see the list of all active subscriptions - note that expired subscriptions will not appear on this menu. If you tap on the name of the app, you can see additional information about that subscription, including the expires on/renews on date. From this screen, you can change the payment method for a particular subscription as well as cancel subscriptions.
At this time, subscriptions and subscription details for Google Play content are not available on the Google Play website - subscriptions must be managed from the device itself.
If you get a new device or perform a factory data reset on your device during your subscription, you simply need to re-install the app where you purchased the subscription, and as long as you’re using the same account you were before, you’ll continue to have access to this content. In other words, you will not need to re-purchase your subscription if the app to which you’re subscribed is uninstalled for any reason.
To cancel a subscription from your device:
Google Play Terms of Service