Do a "list usa extension xxxx" (xxxx being his number) and see if someone has an appearance of his number. They can from that appearance use the system wide feature access codes to activated it. Also under the "ch fea" look for the
Code
  Remote Send All Calls Activation: 185    Deactivation: 186
You can use this to deactivate SAC on his phone from your phone, if you give yourself console permissions in the COS field.

Mike Jones
"A people that values its privileges above its principles soon loses both."
- Dwight D. Eisenhower (1890-1969), Inaugural Address, January 20, 1953