Cancelation of Illustrator

If you didn't intend to use Illustrator for the full year, you should have purchased the costlier month-to-month plan which can be cancelled at anytime. 

To avoid an early cancellation fee, wait until your 12th month of service to cancel.  Or cancel now and pay the 50% fee.  Your choice.

How do I Cancel my Subscription?
https://helpx.adobe.com/manage-account/using/cancel-subscription.html
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Subscription & Cancellation Terms:
https://www.adobe.com/legal/subscription-terms.html

CONTACT ADOBE SUPPORT:
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Online Chat: https://helpx.adobe.com/contact.html?rghtup=autoOpen
Phone M-F, during normal business hours: https://helpx.adobe.com/contact/phone.html

You can plead your case here and see if they will allow it:

Adobe Customer Service (make sure to sign in to your Adobe account first and allow popups on your browser) :
https://helpx.adobe.com/contact.html?rghtup=autoOpen will automatically open the chat window.
Type "Agent" in the chat box to bypass the chatbot and be connected to a person.

You may also be able to contact Adobe by phone:
https://helpx.adobe.com/contact/phone.html

You agreed to a 1 year contract - When you 'click to agree' to the subscription terms while buying a subscription, that means that you really do need to read BEFORE you enter your credit card number to buy a subscription... See this page for more information, including a yellow highlited section from the subscription page https://community.adobe.com/t5/account-payment-plan/cancellation/m-p/12153645

So if you cancel early you pay 1/2 of the remaining time