Your HBO GO subscription auto-renews at the beginning of your billing cycle and is managed through your iTunes account.
As your subscription is managed by your Digital Store, through your iTunes account, for cancelling your subscription you may follow the steps explained by your Digital Store by clicking here.
* You must access or have access to the Digital Store account from which the purchase was completed.
** You should receive an email from iTunes confirming your cancellation. You can continue streaming until your subscription expires at the end of your billing cycle. Once your subscription expires, you must renew your subscription to continue streaming.