Listing all Teams assigned phone numbers
At the time of writing, this does not yet seem possible with Graph API, and requires the Teams Powershell module instead.
Open PowerShell, and install the PowerShell Teams module:
Install-Module -Name MicrosoftTeams -Force -AllowClobber
Connect to the Microsoft Teams service:
Connect-MicrosoftTeams
List all users and their assigned numbers. Export to CSV if needed:
Get-CsOnlineUser | select DisplayName, UserPrincipalName, LineUri | Export-Csv -Path TeamsNumbers.csv