If your domain names are registered with us but your website hosted elsewhere and you want to update your DNS Nameservers then you can manage this yourself very easily from your Client Area.
Log-in to your clientarea.php then, from the main page click on "My domains" which will present you with a colour-coded list of your domain names based on their status (Active/Expired/Cancelled)
Next to each domain name you will see a "View More" icon allowing you to "Manage Nameservers" or click on "View Details", click this and you can now see all of the relevant details for this domain name and access everything needed to manage your domain name.
To change and/or update the DNS Name servers simply change the current name servers listed in the boxes in front of you and click the "Save changes" button.
That's it, now just wait for your DNS to propagate around the internet.