Removing Phone Calls from Calendar?

How do I remove a phone call from a calendar?  Our advice desk log all of the calls they receive and each one is showing up on their calendar.  It does not matter if the call is marked scheduled or completed. If you do twenty calls when you look at the calendar, they are all there plus your meetings.  By making them non-timed calls, we can at least group them.  Making them private will exclude them from everyone elses view but the people who are complaining are the people who are taking the calls.  It dramaticly changes how their calendar