The registrant of a domain is that domain's legal owner, and can modify or transfer it at will. This is why it's so important for us to ensure security around the process of changing registrant details; it's actually a legal operation, rather than a technical one.
So when there are changes in an organization, it's important to reflect these changes in the domains that may be relevant to that organization.
Note that you should use legal names (either a real person, or an organisation's name from the companies register) as the registrant.
In light of this, we have a document that must be completed in order for us to securely change the registrant name. Please have the current and prospective registrants fill out the Change of Registrant form found at the link below, and scan to email (firstname.lastname@example.org), or fax, it to us. We can make the changes immediately upon receiving the completed form!