SE C905 SIP Client??

[RadioRaiders]

I finally got my first UMTS phone (shame on me, I've been building UMTS networks since 2001 ) ...and actually I got it mainly for the GPS and WiFi (I love HSPA, but with a USB dongle on my laptop, not on my phones tiny screen).

Anyway, has anyone used the SIP client on the C905? It seems to be very lacking. I looked at a User Guide for a Nokia s60 and was impressed with the capabilities (could select codec, STUN server, etc.) With the SE C905 you can only enter:

...and that's it (not even a STUN server! ) The User Guide says nothing except this screen exists I connected to my home wifi after configuring the parameters above with my sipphone.com account details and dialed a SIP number, but it tries only with GSM/UMTS. I don't know how to call with the SIP only I couldn't receive a SIP call either. Do I need to install something else (ie: a Java SIP client?) But then why would SE include the SIP feature in the phone without it fully working? Ug...

...the GPS and wifi works great tho