UPDATE...
I took the time to follow the white paper I posted earlier in this thread. We went through all 4 lines and adjusted the volume levels on the gateway until the static and echo disappeared. It took some time, but had to be done. Since the changes, our lines are all clear except one still has some occasional echo or static.
Again, our problem only occurred when both calling parties tried to talk at the same time. If one spoke and the other did not, then the call was always clear. Now that we have made the adjustments to the lines, I have cleared it up by 90% (so far anyway). I will continue to monitor and post if anything changes.
Also, during our test, I found that 2 of our 4 lines were noticeably lower in volume (to the outside caller side) than the others. I adjusted those so that the outside callers could hear us more easily. Here is what my current settings are:
PSTN to VOIP LINE1 LINE2 LINE3 LINE4
2 2 1 2
VOIP to PSTN 0 0 1 1
Each line was different a little. Line 3 is the one that is just a little flaky yet, but I will keep an eye on it.
PCTechie