[Serusers] Ser+Media proxy

I have installed SER 0.9.3.2 and media proxy 1.2.1 on the same machine. The machine is on public network. Calls work ok except when I have a UA on a LAN behind NAT calling to a UA that is in the same LAN. In this case I get : +----------+-------------------------------+--------------------------+| username | contact | received |+----------+-------------------------------+--------------------------+| 22000001 | sip:22000001@192.168.1.7:5060 | sip:xxx.xxx.xxx.xxx:5060 || 22000002 | sip:22000002@192.168.1.6:5060 | sip:xxx.xxx.xxx.xxx:2557 |+----------+-------------------------------+--------------------------+The number that takes up port 5060 on the NAT server,which is 22000001 can call the other UA but not the other way round.22000002 can only receive calls.Please help me,KM