Hi,
To enable a user for Phone System Voice and voicemail, you'll need to perform some initial steps, like checking to see if the Skype for Business Online Connector is deployed on your servers and enable your users for hosted voicemail.
Check the commands and verify whether it is enabled and setup correctly on your tenant, there are policies that needs to be configured :
enable-users-for-enterprise-voice-online-and-phone-system-voicemail
Hope this helps.
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