We run a Freepbx server and it seems to be configured properly. Recently My boss reported that he received couple calls on his ext (which is forwarded to his cell phone number). When he asked caller how did he get his number, caller said he did not press anything on IVR.
The /var/log/asterisk directory. The logs themselves start with ‘full’ and there will be multiple versions as the file is rotated. The ‘grep’ command will help considerably.