The registrant contact is the person or organization that owns a domain. It's important to keep registrant contact updated in order to prevent errors and ensure that domain ownership is secure.
The first step in changing the registrant contact for a domain is to find out who owns it. To do this, you can check the WHOIS database or contact the registrar directly.
Once you have the name of the owner, you can change it using your registrar's tools or by contacting them directly. If you're changing a name server, be sure to update DNS records as well.
