SIP to SIP (peer to peer) call with ATA adptor

[sourdate]

Hello,
I would like to know how to make a SIP to SIP call within the Voxalot. My friend and I each have an Voxalot account setup and each of us uses an ATA SIP adaptor configured to use Voxalot and hooked up to a regular phone. I can see the VOIP light is on on my SIP adaptor and test the *600 number with success. SinceI can't enter the @us.voxalot.com on my phone, I just dial my friend's Voxalot 6 digit userID but the call won't go through. So what should I do? I thought since this SIP call is within Voxalot network, the 6 digit userID should be sufficient. Guess I am wrong. Also, if I want to maek SIP to SIP call other people using GizmoProject, how do you enter the SIP URI on my SIP adapter linked phone. Thanks