I've got a CUCM6.0 Pub/Sub setup with a Unity server. Some directory numbers are setup to forward all calls to an 800 number. When the extensions are called, either internally or via a DID or AA transfer, the call connects but there is a loud buzzing noise making the real audio barely audible. If I change the forwarded number to something else, a non-800 number, it works fine. I've tried multiple 800 numbers with the same result. Also, calling the 800 numbers directly (without forwarding to them) from the site works fine.
I believe that this probably an issue with the service provider, but am I missing anything on our end?