Need help with one way audio issue. I have a school district, multiple buildings all running IP phones off a virtual MCD 3300 . I'm only having issues with 2 schools when an intercom call is made they get one way audio. It's always school B that can't hear school A. Also if school A calls out on a trunk to school B the audio is fine. I'm sure the problem is in the customer's network, but I don't have the knowledge to direct them on the problem. Thanks in advance.