We have a new client that implemented last week. They are experiencing audio problems on the system. Basically the extension rings and the user picks up the phone using either a headset or the handset itself. The caller hears the person who answered the phone, but they also still hear the extension ringing in the background. Users have also said that they can sometimes hear what sounds like another conversation while they are on a call. Not clear enough to make out, but it's definitively some one talking. It doesn't happen on every call, and it has not happened on every extension, but it is annoying for the caller obviously. If the caller hangs up and dials back in to the same extension, the ring echo is still there. If they call back and hit a different extension, the echo may or may not show up again. Any pointers on where to look next would be appreciated. I have checked and unchecked the "pbx delivers audio" with no difference. Software: Windows 2008R2 (Virtualized; 4CPU, 20GB RAM) 3CX version 11 SP3 CBeyond 10MB converged Circuit with 48 active sip trunks. Hardware: Grandstream 1450 with latest firmware.