http://discussion.forum.nokia.com/forum/showthread.php?s=&threadid=50544&highlight=%2Aanswer+call%2A

Handling incoming call is done by the Active Object mechanism.
you have to create your oen active object (derived from CActive) , use RLine::NotifyIncomingCall method to let the system know that you want to be notified on this event, register your active object to the thread's active-schdulare (by using ''CActiveScheduler::Add(this)' inside of your object), and finaly, implementing the 'RunL' method (derived from CActive) in your object. the 'RunL' method will be called by the framework when the incoming call event will occure.

you can call again to 'CLine::NotifyIncomingCall ' from inside your 'RunL' method to register to this event again.

You can find more information in the SDK, read about:
1. RLine, RPhone and RTelServer.
2. CActive.

Finally Reject incoming call is solved!!

/*** it should be called in constructor of CActive Base Class ***/
void CAnsPhoneCallWatcher::RunL()
{
if(iStatus.Int() != KErrNone)
return;


switch(iState)
{
case EWaiting:
{
//_LIT(KMessage1,"Before Notify");
//CEikonEnv::Static()->InfoWinL(KMessage1,iCallName);
iLine.NotifyIncomingCall(iStatus, iCallName);
iState = EAnswering;
break;
}
case EAnswering:
{
iLine.GetStatus(iCallStatus);
if( iCallStatus == RCall::EStatusRinging )
{
User::LeaveIfError(iCall.OpenExistingCall(iLine, iCallName));
//iCall.AnswerIncomingCall(iStatus);
iCall.HangUp() ;
iCall.Close();
iLine.NotifyIncomingCall(iStatus, iCallName);
}
//_LIT(KMessage1,"After Answering");
//CEikonEnv::Static()->InfoWinL(KMessage1,iCallName);
iState = EAnswering;
break;
}
}
SetActive();
}