Login to wp-admin diverts to old domain

I am managing a client’s website which used to have the login at the .org version of his domain. It is now on a .com.au version and the site was copied over from the old server to the new.

On the old server it was set up in the dashboard so that to view it was the .com.au version but the site was actually on the .org version.

The client does not have login access at the domain registry for the .org and we haven’t been able to get access to update the name servers and want to let it go. Is there a way via cpanel to update the wp-admin login so that we can get in via the .com.au version of the domain?