Hi,
  I have a sim from Saudi Arabia which Iam trying to use to establish CSD call in US.THe roaming nework there is AT&T.Iam able to recieve a CSD call made from Saudi on my phone but when I make a call from US,the reciever who is in Saudi detects it as a simple voice call.
I think that somewhere in he network, he call is being converted as a voice call so the reciever detects the incoming call as a voice call.Is this true.If yes then how can I establish a link with my current setup.