No access to router - Can STUN setting be added to compensate?

Asterisk Ver. 11.10.0

Shortly I will be using a WiFi network, for my Internet connection, where I have no access to the router. Hence I can do no port forwarding. From my experience this can mean no audio. I’m hoping that STUN may help but I do not know how this can be set in FreePBX - or Asterisk itself.
Can anyone advise please?