FWIW: I do not have the network tab either..

But the link : https://secure.voipo.com/preferences/network
does indeed take me to the network settings.

Suspect the Vpanel has changed between you signing up and me signing up.
I'll bet us newbie VOIPo'ers have a more generic Vpanel so we don't screw things up.
You old timers already know what not to touch.. LOL