I have an AWS ec2 instance with Kamailio and rtpengine configured. I am having a challenge of no voice on calls. I have sip client on my mobile phone and soft phone on my laptop and the two are on different networks behind nat. Signaling is working fine but there is no media and when I check on on the SDP the call logs are showing private ips instead of public ips : o=- 3 2 IN IP4 192.168.1.33 and c=IN IP4 172.31.36.50. I understand this is a NAT issue but I am failing to see where is the challenge. My rtpengine seems to be working fine .

Most likely you need to use the "advertised address" notation in your interface config as on AWS generally you don't have the public IP address bound on a local interface. So something like

interface = external/172.31.36.50!13.246.88.123;internal/172.31.36.50

Cheers