My mother has a windows phone and when I called her on WhatsApp it rang but before it said voice was not available. I have not seen any news about it. I am unable to reach her so I can't confirm.
probably a false ring before whatsapp servers realises the other party is using unsupported version.
I searched for an update and got no update. Nope, no voice at the moment.
The iOS app did get updated today (or yesterday) adding that very feature.
It can only be a couple of more years until it will be added to Windows Phone :winktongue: