XCX ripping wheeze old boy.
However be careful if your are NOT ex CX. Large companies have a habit of spending inordinate resources and bringing their IT departments to a halt for weeks to trace stuff like that. Some companies have even been known to go into the more illegal side of searching just to find a whistle blower or a thorn in a senior manager's side.
Hacking into the systems of crew hotels has been reported from one airline, to gain access to phone records during an industrial dispute - illegal in that particular country. The anonymous caller number system in Hong Kong works for the receiver, but if your company has good contacts in PCCW it is said that it is a matter of a moment to have the dialer revealed.
So be careful out there. If you are that good at comms cloaking, you should be working in IT anyway.
Only the paranoid survive.