Goip sip trunk, no sound

some weird issue i got here
i have a freepbx server on my pc
it has one extension , phone that is connected to the same router as the computer with the freepbx
and in addition theres a goip gsm gateway sitting there too

im currently in another country, with my phone which has zoiper on it set to work with the 2nd extension i have.
now if i call between extensions i have no problems, i can hear the tone when ringing, can speak on the phone normally, all is well
but when dialing out or getting calls to the gsm sim card which is in the gsm gateway, the calls are getting through but i dont get sound whatsoever, no ringing tone or voices.
now when i was at home next to it, on the same network, it worked just fine, gsm calls and everything sounded perfect
now when im out it giving me hell
whats weird for me is that if this was a port forwarding problem the extension wouldnt work neither right ?
in any case i tried DMZ to my server just to see if it makes a difference, same same
where i go from here ?