@OKA Netlify’s staff need to manually remove it from the previous account.
You can try creating a ‘helpdesk ticket’ using the form here:
For ‘What kind of help do you need?’
I suggest that you try ‘Site/DNS Transfer’
They may require that you verify ownership of the domain.
You can do so with the Support Guide instructions here:
https://answers.netlify.com/t/support-guide-another-site-is-using-this-domain-verifying-domain-ownership-for-netlify-production-domain/13765