If your domain is managed in my.rackfish.com:
Log in to your account and select "Manage" - "My Services" - "Domains" in the main menu if you do not see the domain in question.
Click on the domain and then select "Contact Information". All contact details for your domain can be managed here. Some TLDs may require additional time to complete changes, please get in touch with us for assistance.
If your domain is not in my.rackfish.com - contact: support@rackfish.com.