To clarify: I know that it's great if you use Asterix and talk to that, but I'd just like to connect to xnet directly for the moment...
kyhwana2: You need to be running asterisk somewhere (Probably at home, but anywhere should work) that the SIP client on your phone runs.
(So no, you can't do what I think you want to do. You have to setup asterisk with your vfx details and then your phone connects to your asterisk server)
You don't need to run Asterisk - with an Asterisk profile you can connect any SIP device to VFX whether it be a softphone or hardware.