Unless you send out individual caller ID per extension, the phone company won't be able to tell you anything except when the call was made. Only a cost accounting system would be able to tell you where the call was made from.
Otherwise, the horse is out of the barn, too late to close the barn door now.
You could setup account code restrictions and reduce COR calling permissions from calling certain areas. Then when someone tries to call out to these restricted areas, they have to put in an account code to complete the call.
- Stinney
"Scire ubi aliquid invenire possis, ea demum maxima pars eruditionis est"
"To know where to find anything is, after all, the greatest part of education"