Verifying the ownership of my custom domain

Netlify site name:
Custom domain:
The error while adding my custom domain:

Another site is already using this domain
Domains must be unique across Netlify. Currently another site is using this domain. If you don’t know which site, please contact support for guidance.

This domain is being used from another netlify account. I own this domain now and can’t contact the previous owner.
I’ve added the required fields as a TXT record as specified here: [Support Guide] "another site is using this domain" Verifying domain ownership for Netlify custom domain

Please verify my ownership of this domain and free the domain.

This has been handled in the helpdesk.