Have an OfficeServ 7100, and all we did was change data providers. We're using SIP from 2Talk and switch from CalWireless to AT&T for data services. AT&T says all ports are open for our use, and most ports are open with exception to 6000 and 5060. So if we just changed carriers and the carrier has changed their database to reflect the new public IP and we have changed that on the Samsung (Private w/Public) why don't we get through. Outbound is silence for 5-7 seconds and busy (display says CO Hung Up). Inbound, the system rings, we pickup the phone and there is no audio; as if no connection, but you can hear the person hangup from inside.

Can anyone out there let me know what we are missing. AT&T tech support is non existent and they say all ports are open.

You need to confirm AT&T is telling you the truth and not blocking ports. It seems clear they are.

Just a quick check list for you:

-In MMC837 (Carrier Options - SIP Service Available = Yes?)
-Did you update your new public IP address from 2Talk (SIP carrier)?
-Audio issue usually is port issue, but can you make outgoing or incoming calls?