You can change your G Suite primary domain with an existing sub domain.
You may wish to do this to reflect a change in your real organisation or company such as a rename or rebrand.
The main benefits for most organisations will be consistent branding in Drive shares and Calendar invites, which always shows the primary email address of the user.Adopting the domain may require you to then change user accounts by renaming them to use the new primary domain and can have implications for things like:
3rd party Apps
We therefore recommend that you plan any changes carefully.
The sub domain must already be added and verified and must be a subdomain and not a domain alias.
The change is simple enough via the admin panel and requires your account to have the Domain settings privileges (or Super Admin) to carry it out.
In the Admin Panel
Navigate to > Domains
Click Make Primary (to the right of the domain name you want to use as the primary domain)
Click Change Primary Domain
We recommend you read the advice in this G Suite Support Guide before making any changes to your primary domain.