You can use RTMT if using MGCP
or show isdn commands for H323, SIP
* Unallocated number
* User busy
* Out of bandwidth
* Gateway fails to respond to the call setup request
Sometimes this error may be misleading, and there are ocassions in which Re-route flags behavior when we get a busy or unallocated number attempt to look for another GW to route the call, and thus generate error above.
You can check the value for
Stop Routing on User... under SP to get rid of those alerts depending if my description matches what you are seeing