Refund

The terms are the following:

• First month is free
• Second month gets billed.
• If you cancel the first 14 days into the second month, you get a refund.

To cancel your subscription, please look here: Cancel your Adobe Stock membership 

If you have problems to cancel, you can 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! If the chat window fails to open, or is non-responsive, use a different device to start the interaction.
Support phone numbers may be found here: https://helpx.adobe.com/contact/phone.html. Please note that phone charges may apply.

(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)