You would have needed to cancel your free test as stated in the terms and conditions. You can still cancel free of charge, if your paid subscription is in the first 14 days. Thereafter, you have a valid annual subscription that can be cancelled anytime by paying an early termination fee of half of the remaining due. According to the terms, you are not eligible for a refund after those 14 days.
Cancel your Adobe Stock membership
If you can't self-cancel, you need to contact Adobe customer care. 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.
Support phone numbers may be found here: https://helpx.adobe.com/contact/phone.html. Kindly note that phone charges may apply.
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.
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