On top of what Christian said, you also have to deal with legal issues. In the US, unless you specifically spell out this policy and notify BOTH parties on the line that the call can be monitored at the beginning of the call, you cannot legally monitor the call.
A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008
But no longer in 2009...