[Freeswitch-users] Auto Changing port

Hi I'm using openser+FS, FS as B2BUA, so, the call goes to openser and then to FS. The problem is, when customer is behind nat, some times work and some times not. When freeswitch show this message, work: 2008-10-17 09:50:25 [INFO] switch_rtp.c:1289 rtp_common_read() Auto Changing port from x.x.x.x:1122 to x.x.x.x:1244 So, I can make 10 calls from the same voip, in sequence, and sometimes work and sometimes not, all time that work I see this message. There are any way to force FS to do that all time? Thanks Thiago