child subscription?

Your son has now learned 2 very important lessons

1 - something for nothing is a myth

2 - NEVER give a credit card number if you don't know what you're doing

2 free months of service is an incentive to join for 12 months and receive 2 months free. 

I urge you to supervise your son when making purchases so he understands the terms he's agreeing to. If child is under 13 years of age, an adult must make the purchase for him and agree to the annual terms of service.

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

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

that child must have been old enough to understand how to input credit card information and agree to a one year subscription that included a penalty (=1/2 the remaining months of the one year subscription).

you can contact adobe support and see if they'll make an exception for you, but they are not obligated to do so. 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

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.

p.p.s you can also use phone (but chat is usually quicker), https://helpx.adobe.com/contact/phone.html

p.p.p.s. you can also use twitter to tweet @AdobeCare.