I have an Aastra phone and on 1 of them when I dial out I hear it rings. However the other party can't hear me and I can't hear them. All I can hear is myself (echo). I have port 9000-9500 opened in my firewall. I connect to OVH with SBC. On another Aastra phone when I dial out it rings for a few seconds and automaticly disconnects. On incoming, just a brief ring burst. Can't figure any of these out. And these phones are legacy supported phones.