How to hang up a modem, that is already in use?

How to hang up a modem, that is already in use?

I know the modem COM port number.
It is connected using Win2k RAS (remote users are connected to the PC)
How can I disconnect them?!
Is there any RAS API?
Can I use modem driver to hang up it?

Thanks.

Declare Function RasHangUp Lib "rasapi32.dll" Alias "RasHangUpA" (ByVal hRasConn As Long) As Long