i can't cancel my free trial adobe stock

Look here: Cancel your Adobe Stock membership

If however you are on the transition for a paid subscription, you will be able to cancel after that. You will be charged and reimbursed. If your card has payement issues, you can't self cancel neither.

If you are not in the transition to a paid subscription (that means that currently your payement options are being processed), I suggest you contact Adobe customer service. Adobe customer care can be contacted here: https://helpx.adobe.com/contact.html - click the small callout at the lower right of the screen and type "agent".