I want to cancel my adobe illustrator subscription without updating my payment method, how?

If you have outstanding amounts, you need first to pay, then you can cancel.

If your payments aren't current, the online system won't cancel your plan, sorry.

https://account.adobe.com/plans

There's a 50% early termination fee for cancelling annual plans before your 12th month of service.

Subscription & Cancellation Terms:
https://www.adobe.com/legal/subscription-terms.html

there are 3 ways to contact adobe; chat, phone and twitter:

chat:
use a browser that allows popups and cookies, and click here, https://helpx.adobe.com/contact.html?rghtup=autoOpen
in the chat field (lower right), type AGENT
be patient, it can take quite a while to reach a human.

phone:
https://helpx.adobe.com/contact/phone.html

twitter:
tweet @AdobeCare

p.s. if you're contacted by anyone (via email or private message), it's much more likely to be a scammer than an adobe representative. ie, double check for an employee badge if contacted in the forums and look for an adobe.com domain in the email address if you click reply to an email. then check again and be very suspicious. any other method of contacting (or offering to contact you) is almost certainly a scam, https://community.adobe.com/t5/using-the-community-discussions/staying-safe-in-the-adobe-support-community/td-p/12919684/redirect_from_archived_page/true

Please contact Customer Care. https://helpx.adobe.com/contact.html