Scheduled flights

How come scheduling is so hard.  The flights wont take.  Then I reschedule them.  Then much later I have the same aircraft with two or three flights with the same  flight number. Same departure times or off a few minutes.   They are all Getting booked . This is why the DC9, that  I cancelled the lease and closed the schedule and the flights got screwed up. I got more flights with the same number.   on the same plane. And a cancelled lease plane assigned.

Do I got to close the account every time I want to change  an airplane or change flights . or something. 

of course not - but it seems you were doing here something wrong again