So you hear the echo, not the people on the other end of the line, right?
What you might try doing is tweaking the echo-canceling values first.
The thing to do is get a 7960 IP phone, call one of the numbers that IS echoing, use the 7960 to generate the testing tone, and go from there. Playing with your attenuation before you've identified a solid problem is a bad, bad, bad, bad, bad idea.
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...