Login to the control panel - https://my.firstserv.com/clientarea.php Β» Account Login Β» My Domains
From the My Domains page, click 'view details' for the relevant domain, and then click 'contact information'. From this page you can alter the contact details.
NB - for .uk domains you cannot change the registrant company name this way. To do this, please go to Nominet directly http://www.nominet.org.uk/registrants/maintain/transfer
