The telco is definitely sending the disconnect back in this case. I had this issue and it turned out that when I place the call the telcoside is expecting the calling number to be one of the DIDs that belongsto me. simply because this was not the cas...
I had the very same issue and the culprit was that the IP Address in the dial-peer that was going from the gateway to the call manager add the wrong ipv:4 address for Call Manager. Simple issue but always pays to double check the IPs, maybe even chan...