Failover on Freepbx problem

When my trunk provider cant connect to my FreePbx, I get a txt message.
Today something was wring with my Freepbx and callers were getting “The number you dialed is out of service…” The Admin console was not showing an error and a reboot solved the problem.

I would like to get a notification if the “Number you have dialed…” message ever plays so I’l know if this happens again.

Any way to do this?

PBX Firmware: 1.813.210.58-1
PBX Service Pack: