Hello @john.pascoe,
Welcome back to the Auth0 community!
If you want to just change the company name displayed, you can change it in the Settings section of the Account Settings(https://manage.auth0.com/#/account ) page.
If you want to change your custom domain to a new one please check the following Knowledge Solution: Change Custom Domain to a New One
Also, please make sure to look at this documentation regarding Custom Domains: Custom Domains
I hope this was helpful and if you have more questions, don’t hesitate to come back to the community.
Thanks,
Tudor