Hi @Troy Rainey ,
As mentioned in this article, to assign numbers by using PowerShell in Microsoft Teams, please use the Set-CsPhoneNumberAssignment cmdlet instead. For the situation you described, you can run the commend below after replacing the identity and phone numbers:
Set-CsPhoneNumberAssignment -Identity "user1@contoso.com" -PhoneNumber "+123456789;ext=1002" -PhoneNumberType DirectRouting
More details, hopefully you can find the document below helpful:
Enable users for Direct Routing
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