In my case, when first on FTTN my VOIP did not work. A call to TPG fixed that. I did not have to change any settings on my Vx420 (possibly TPG did it remotely). I am now on FTTP and for me voice was via the NBN NTD. Again it needed a call to TPG to get VOIP to work. So in both cases for me the call was required. A mod here might action this for you via a PM.
