Re: While customizing Office365 email accounts to use @yourcompany.com I cannot select any of the @yourcomapny.onmicrosoft.com accounts.

Hi William,

Based on the current situation, I would like to confirm whether @paget-brown.com has been verified.

Please refer to the article below to check it.
Add a domain to Office 365

In addition, you could also follow the steps below.
1. Go to users & groups.
2. Add a new user.
3. In details> User name, check if you could choose @paget-brown.com as the domain of the email address.

If your domain hasn’t been verified, please verify it and try the steps again.
If the issue persists, please provide me with some screenshots for further analysis.

Thanks,
Kid Yang