1. Adding SBC in Direct Routing

In the left navigation of Microsoft Teams admin centre, go to Voice > Direct Routing, and then click the SBCs tab.

Click Add.

Enter a FQDN for the SBC.

Make sure the domain name portion of the FQDN matches a domain that's registered in your tenant, and keep in mind that the *.onmicrosoft.com domain name isn't supported for the SBC FQDN domain name. For example, if you have two domain names, contoso.com and contoso.onmicrosoft.com, use sbc.contoso.com as the SBC name.

When you're done, click Save.