Free Trial Bill

The stock trial is for one month. But even if you have an application trial, it's more or less the same procedure:

Cancel your Adobe Stock membership

For applications:

How to cancel your Adobe trial or subscription

You will get refunded if you cancel in the first 14 days of your subscription.

If you want 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! 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)

Please note: Teams/Enterprise customer should use the console to contact support.