Problem with Nokia E90 when making and receiving calls.
 

I have recently signed up to Voxalot and use PennyTel as my VSP. I have configured Voxalot on my Nokia E90 as per the instructions on the Voxalot website.
I have then made some internet calls through my mobile using Voxalot and I have noticed that the call goes through but I am not able to hear the ring on the other side or the other person speaking. But the other side, when the call is answered, can hear me very well. I have also received a call via my SIP URI and it's the same story again; I can not hear the person calling me but the person calling me can hear me.
Is there something in the settings that I need to change?
I have downloaded Fring and have put the Voxalot settings in th Fring app and making outgoing calls works fine. Is there somthing in the Nokia E90 setting that I need to change? Please help.

Your router's NAT is the problem, SIP does not do well with crappy NATs. Fring and Skype do things a little differently, and handle crap NAT configs a little better

But Bridonca, my Nokia E90 is not connected to my home's wifi router. My mob's connected through a data plan that I use through my service provider.
Any ideas as to how I would have this solved?

Look for "Sipsettingtool" on Nokia site and install it if not done already.

That is probably worse! :) Cell phone providers are not exactly the most enthusiastic people when it comes to 3rd party VOIP. Shockingly, they even do nasty things to the VOIP to make it difficult to work properly. I do not know if that is the case for you.

However, 441516 has the better idea. Nokia's seem to be flaky with the default settings, but that package is supposed to do wonders.

Thanks guys for the responses. The Nokia Sip setting has helped. I hope it keeping going like this. Thanks again.