You have taken an annual subscription for Adobe Stock. As stated in the terms and conditions, you got a 30-day free test subscription. After the first payment, you had 14 days to cancel free of charge. Thereafter, you can cancel anytime by paying an early termination fee of half of the remaining due. There is nothing in the conditions that says that after paying the first month, you can cancel free of charge. If you wanted a subscription for the month, cancellable each month, free of charge, you should have taken a monthly subscription.
I suggest you should contact Adobe customer care to discuss your options. Adobe customer care can be contacted by beginning a secure chat session at https://helpx.adobe.com/contact.html?rghtup=autoOpen. Pop-up blockers need to be disabled, you need to accept cookies! If the chat window fails to open, or is non-responsive, use a different device and/or browser to start the interaction.
For support via Twitter:
https://twitter.com/AdobeCare
(see also here: https://community.adobe.com/t5/creative-cloud-services/how-to-contact-adobe-support/td-p/11875703 or here
https://community.adobe.com/t5/account-payment-plan/how-to-contact-adobe-support/td-p/11843852)
Important: Adobe does NOT contact you unsolicited by e-mail or direct message. If you get contacted by direct message from a person, claiming to be an Adobe employee, look at that profile and look, if they bear the “Adobe Employee” marking under their name. Adobe support does not use Skype to give you support.
If in doubt, ask the forum.