I recently decided to configure VoIP on my (recently) new N97 mini (by the way, I'm really impressed by the quality of the phone. Going to keep it for the next several years, because he satisfies me completely). Actually, I had already configured my SIP-profile some time ago (I have an account at "CheapVOIP"-provider), but I had real problems with using it, because when I tried to use it via "Sipgate", it simply didn't work - I couldn't make any call. So, I decided to fix it and made some search in google. In order to configure the VoIP on N97 mini, you MUST have this file:
Earlier it could be downloaded from Nokia site, now (August 2014) you should google for it. Download it and install like any other ordinary application. After you installed it, you should have new menu item "Advanced VOIP Settings" here:
Settings -> Connectivity -> Admin. settings -> Net. settings.
Now you are able to configure VoIP on your phone:
1) configure your SIP-profile as described in my earlier post about N95;
2) now go to "Advanced Voip Settings" menu item. Click on it, and choose "create new service". You will be asked for the SIP profile, which will be used as a basis for the new service. Choose your desired profile and wait a couple of seconds;
3) now if you go to the menu item "Voip services", you will see your new service.
That's all. Noe you can use VoIP-feature of you N97 mini.