Take existing phone call private

[dsvick]

There is nothing in the manual on this nor can I find anything in an online search. Is there a way using the main screen, to change an existing phone call from bluetooth, over the cars speakers and microphone, to a private call? I can probably do it using my phone but it isn't always safe to do so using the phone, my old car's radio had a button you could use to toggle private vs bluetooth.