How to route audio (VoIP phone calls) to sound card channels

Question

Hello,

I face with a problem while using Ozeki VoIP SDK along with a special 8-channel sound card (Gigaport).

I try to describe the problem in more details. So, I want audio in respect of all calls to be routed to one of the channels on the card.

It works in case of the first two calls, but audio is not routed to the preferred channel for the other calls.

I have no idea where to start in solving the problem. Where is the error? In the sound card? In the controller? Or is it SDK issue?

The following method is called at the end of each phone call:

private void stopSpeaker()
{
connector.Disconnect(mediaReceiver, speaker);
if (speaker != null)
{
speaker.Stop();
speaker = null;
}
mediaReceiver.Detach();

Please give me some ideas or help me to get moving, because I got stuck here... :(