How to turn off subscription autorenew ios 8.1?

Tapping on your id in Settings > iTunes & App Store (that is the account that you subscribed to it ?) and logging into the account should let you turn its auto-renew off : Manage your auto-renewing subscriptions.

If not then try contacting iTunes Support and see if they can find and turn it off : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption

You are being charged through iTunes, and you only have the one account ?

If it's not showing on the screen for stopping then try contacting iTunes Support and see if they can stop it for you