Dear All,
I tried to put the SIP settings into my phone and access my company wifi but it get connect but no voice, don't know exact reason may be my firewall but all port is open dont know if VOIP is blocked from ISP.
so after that i keep searching and finally i got solution to access actionvoip on your N900 use fring messenger and login and go to add on and select SIP and put actionvoip settings and then go to dial pad and start calling..

Regards,
Huzefa M Sultan