Ask for refund of stock

Check in https://account.adobe.com/plans to see what plans you have. If you have a stock plan (that is a separate plan from Creative Cloud), cancel it. As the trial started yesterday, you are still good for a refund.

If that does not work out for you, contact Adobe Customer Service, as @kglad suggested.

make sure you're aware of the cancellation terms by selecting your plan type (at the top of the page here), https://helpx.adobe.com/manage-account/using/creative-cloud-subscription-terms.html

for info on how to cancel your subscription, this page describes the few steps involved, https://helpx.adobe.com/manage-account/using/cancel-subscription.html

if you want to cancel but are unable to follow the steps described in the "how to cancel page", contact adobe support.

there are 2 ways to contact adobe; chat and twitter (now x):

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.

twitter/x:
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.