Help to solve problem native Nokia SIP client for E71 and Voxalot

Hello,
Colleagues, please help to solve problem with native Nokia SIP client for E71 and Voxalot VOIP provider. I use 3G connection with my mobile operator Megafone in Saint-Petersburg.
I have to use VOXALOT (SIP broker) for works with two VOIP Providers for cheapest rates plan for landline and mobile phone in Russia. When I call my mobile subscriber he has to see my mobile Callirer ID.
I use Beatamax clones Voipraider and Webcalldirect. When I set up separately native SIP client E71 for Voipraider and Webcalldirect with this [URL="http://freevcalls.blogspot.com/2009/06/nokia-internet-telephone-betamax-sip.html"]instructions [/URL] than call session on both case with subscriber are established, the quality of sound is very qood.
I spent many time for correct setting Voxalot for E71 - in this [URL="http://faq.voxalot.com/action/view/Nokia_Configuration_Settings"]instruction[/URL] I must change type of transport from UDP to "auto" or "TCP" in Proxy server and Registrar server - when I set up type of transport in these section to auto than call session was established but I and my subscriber didn't hear each other. I discussed this problem in [URL="http://forum.voxalot.com/voxalot-support/4656-calling-problem-voiprider-through-vaxalot.html"]Voxalot forum[/URL] but problem hasn't solved yet.
Description on problem.
Now I am using [URL="http://forum.voxalot.com/27032-post13.html"]this setting [/URL] with SIP naive client Nokia E71
When I call my subscriber (I replace first symbol + in number to 00) my subscriber see my CallierID, connection ere established, we either hear each other very well. But after 31 - 35 second after conversation my subscriber dissconected, but on my E71 call session established and I must manualy close call session.
Tips - I install Fring and Nimbuzz on E71. I wrote Voxalot setting (Iser ID, name registration server, password) for integrated SIP clients in these applications - now VOXALOT works, call session doesn't disconnect, I can speak with my subscriber long time, but quality of sound is the worst than native SIP client setting for Voxalot or VoipRider or Webcalldirect.
I think that problem in network setting - I don't know where and which parameter I have to change...
Mobile E 71 with latest firmware (I updated firmware yesterday through Nokia Software Updater v.2.4.6 en from Nokia official Internet web sight)
Installed Nokia SIP application SIP VoIP 2.x Setting - this is file SIP_VoIP_Settings_v1_2_en.SIS from [URL="http://www.forum.nokia.com/info/sw.nokia.com/id/d476061e-90ca-42e9-b3ea-1a852f3808ec/SIP_VoIP_Settings.html"]SIP VoIP Settings[/URL]
P.S I looked for on this forum about problems E71 and VOXALOT but nothing found.....

Enable RT[b]C[/b]P, see [url=http://www.forum.nokia.com/info/sw.nokia.com/id/2e470bc4-236d-48e2-bc96-977784811af8/Nokia_S60_VoIP_Implementation_Troubleshooting_Guide.html]this[/url] and [url=http://www.forum.nokia.com/info/sw.nokia.com/id/8c94bef3-bc2f-4723-8552-3e95b1c90206/SIP_VoIP_Settings_User_Guide.html]that[/url] for more details.