I'm trying to setup a simple proxy with NAT/RTPproxy.  I have started with the basic cfg file and added nat and forced rtpproxy.  

The proxy is to reside in between endpoints and multiple SIP servers.  Currently calls from endpoints are working great but my issue is calls from the server to the endpoint.  The SIP messages are good until the 200 OK sent from the phone back, Kamailio is not fixing the contact so it's sending the private IP of the phone back to the server so all subsequent traffic is attempting to route to the private IP.  I have tried using the fix_nated_contact everywhere I could think but still no difference.