On the @voice portal:

Once your Microsoft Teams Account has been setup, click on the Connections icon. You will see two domain names in there. These domain names will need to be registered individually in the users Microsoft Office 365 tenant account. You can do this over at https://admin.microsoft.com. For more information on adding a domain in your Microsoft Tennant, please refer to this Microsoft document - https://docs.microsoft.com/en-us/microsoft-365/admin/setup/add-domain?view=o365-worldwide

On the Microsoft Admin Panel:

Once in Microsoft Admin center, go to Settings > Domain page and select Add domain.

From the diagram above, in "1", paste the domain name you received on the @voice portal and click on Use this domain (marked "2").

You will the come to a How do you want to verify your domain? page. Select Add a TXT record to the domains DNS records  and click Continue

You will need to copy the 'TXT value' (as shown in the below diagram marked as "1"), paste it somewhere safe, as you will need that a little later. Click on 'Close' (as shown in the below diagram marked "2"). Don't worry about not completing the process. You can only do that a little later.

Make sure you copy the entire value. From the diagram above the value you should copy is "MS=ms30071687".

Now, do the same for the second domain and copy the TXT value and paste it somewhere safe. Again, click on 'Close' without needing to verify or complete the process.

From the main domain screen, you will see that the process is not completed. Don't worry, we will come back to that in a bit.

On the @voice portal:

Now head back over to the @voice portal and enter the TXT value that you copied earlier, just paste the relevant TXT value to the corresponding domain name and hit update. Give it a few minutes while also keeping an eye on the status bar. Once the status bar is green and says 'Active', you can head back over to the Microsoft Admin page.

On the Microsoft Admin Panel:

Click on the domain name that is marked as 'Incomplete Setup' and click on 'Start Setup'.

You will arrive to the verification page. Click on the 'Verify' button.

You can uncheck all the selections present on the next page as they are not required and click Next and Finish.

Once both domains have been successfully verified and the status shows as healthy, you can proceed to the next step.

Next Step: Activating the @voice Domain