Please help me cancel my subscription

The self cancel is not possible if you have payment problems or at the very verge of the renewal process, when the payment is processed.

Self-cancel: Cancel your Adobe Stock membership .

You need to contact Adobe customer care if self-cancel is not possible. Adobe customer care can be contacted by beginning a secure chat session at https://helpx.adobe.com/contact.html?rghtup=autoOpen. If the chat window fails to open, or is non-responsive, use a different device to start the interaction.

(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)