iPhone call audio to hdmi

In our conference rooms we have TV w/ hdmi ports on the table. During webex/GoToMeeting/other conf apps I connect my laptop to hdmi so I could project sound to tv as its louder/better than my laptop. My laptop mic works well & pickup all conversations in the room.

I wanted to do the same on my iPhone 7+.

I have the webex or GoToMeeting app & have the hdmi adapter.

My screen is projected on TV, but the audio would not.

I tried basic phone call with hdmi adapter, I see my screen on TV but audio stays with the phone, I clicked speaker and audio came out of phone speaker not TV.

If I play youtube or apple music, audio is projected to TV.

Has anyone tried this & make it work? or is it by design or limitation?