Canceling a subscription if didnt sign up for

If you gave your son your credit card you clearly did not supervise him very well

If you did not give him your card, he is a thief

probably not, but you can try. btw, your son didn't just sign up for a subscription. he most likely used a credit card to pay for it.

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 by using a browser that allows popups and cookies, contact adobe support by clicking 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
inform the agent that you want to cancel.

This is a user-based forum, so there is noone here that can help you with subscriptions issues. You need to contact Adobe directly for that. That being said, the terms and conditions are pretty clear about what you can expect:

https://helpx.adobe.com/ca/manage-account/using/creative-cloud-subscription-terms.html#cancel