I solved the problem by setting force_rport, rtp_symmetric and rewrite_contact in global template. I guess this problem occurred because the client wasn’t receiving response from WAZO due to NAT problem.
But the NAT problem remains when my client is in local WiFi. It works perfectly when I use mobile data to connect to server, but in WiFi, the NAT traversal doesn’t works as it should be.
Do you have any suggestion for this problem? I mean without STUN/TURN server.