Accidentally licensed a Premium Image

There is no way you can accidentally licence a Premium asset as a confirmation is asked. So you needed to confirm the buy. There is no method to unlicence an asset.

Presented below are two approaches that may potentially address your issue. Your quest may be successful or unsuccessful.

If you have a Teams or Enterprise account: An administrator for that account needs to contact Adobe support via the admin console, and has to negotiate a refund.

If you have an Individual subscription: You have to contact Adobe support and negotiate a refund. Adobe customer care can be contacted by beginning a secure chat session at https://helpx.adobe.com/contact.html?rghtup=autoOpen. Pop-up blockers must be disabled, you have 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.

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.