How to get the display name of a remote participant when I start a call?

Hi,

I meet some problems when I'm using UCMA 4.0.

I start an instant message call by calling InstantMessagingCall.BeginEstablish(destinationUri, ...), it works fine except after the call is established, the display name in Conversation.RemoteParticipants[0](it's a two party call).DisplayName is an empty string. 

If I let my program to wait for an incoming call, the DisplayName can be shown, but it won't working if I want to establish an outgoing call. Why is that? Am I missing something?

Any help is appreciated. Thanks.