I have two type of echo issues: 1) Echo between extension to extension. We are using Polycom 550 and 650. Why would we have echo between extensions? Not all the time, but it is still annoying. 2) Echo to/from external calls. We are on a PRI circuit and as of last night, I installed the Digium echo cancellation module hoping it would fixes the issue. This morning, one of my user reported echo on his external call. Again, it does happens all the time. Please guide me on how to fix / address the issues. Thank you!