Subskription

You can use this link to cancel your subscription, but you might have to pay a fee for doing so (since the yearly version is cheaper than the monthly one): https://helpx.adobe.com/manage-account/using/cancel-subscription.html

If you want to ask for a refund you will need to contact Adobe directly:

You should contact Adobe directly for help with this issue:
Chat support: https://helpx.adobe.com/contact.html?rghtup=autoOpen
(type "Agent" to chat with a real person)
Phone support: https://helpx.adobe.com/contact/phone.html
There's no email support.

Beware of people contacting you via the forums' messaging system pretending to work for Adobe! Only those with an "Adobe Employee" tag under their name are legit. Also, Adobe will never offer to contact you via Skype, or use an email account that's not under the adobe.com domain...