Issue: need to phone a lot of people. especially nowadays when lots of people are on holidays so have to leave literally hundreds of voicemails a week.

Knocked up little VB.Net app in VS, simple windows form with button, onclick event to play wave file
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
My.Computer.Audio.Play(“voicemail.wav”, AudioPlayMode.Background)
End Sub

It plays sound alright but does not “put it through” the microphone

https://superuser.com/questions/1133750/set-output-audio-of-windows-as-input-audio-of-microphone
found this article and
Go into the “Sound” control panel applet, (e.g. Start -> Run -> mmsys.cpl)
select the “Recording” tab,
Then right-click on and enable the “Stereo mix” device. << did that too but still no luck

we use MS Teams & RingCentral so need this to work at Windows level i.e. to play audio to microphone as if I was speaking.

Any help is much appreciated, thank you

tried playmode background method and sound mixer but no luck