I have tried everything, and I must admit, I give up,

Here are the settings I have used, if someone can shed some light on the subject, please let me know!

It will always just state "internet tel not avail"

There are two menu areas for setting it up which confuses me even more.

[Internet tel] this is just configred ti use the SIP settings specified.
&
[Sip settings]

registrar settings.

sip:alk.italk.co.nz

Realm
none (also tried "italk.co.nz")

User name
649974xxxx

*********

Transport type
UDP

Port
5060

Proxy settings

proxy server
none

realm
none

none