I am afraid that there is no option where you can cancel the Annual membership because it comes with annual commitment.
I would suggest you to contact our chat support http://www.adobe.com/support/download-install/supportinfo/
You contact us on "Twitter" as well @Adobecare
Welcome to Adobe Forum,
You can cancel the Adobe CC with a full refund within 30 days of purchase.
Please check the above for all options to cancel.