You would need to cancel what you have and buy a new subscription
-or by telephone http://helpx.adobe.com/x-productkb/global/phone-support-orders.html
Cloud Plans https://creative.adobe.com/plans
-and subscription terms http://www.adobe.com/misc/subscription_terms.html
HOWEVER... you should contact Adobe to be sure you may cancel without a penalty
Adobe contact information - http://helpx.adobe.com/contact.html may help
-Select your product and what you need help with
-Click on the blue box "Still need help? Contact us"