For some this will make it a little more clear.
For others it may muddy the water.

One person uses 1 channel.
One port gives you 2 channels.
One line cord...... that depends on the voice mail unit.

NAM - one line cord - one port - 2 channels - 2 users
Call Pilot-100 - one line cord - one port - 2 channels - 2 users.
Call Pilot-150 - one line cord - two ports - 4 channels - 4 users.


If CON is the opposite of PRO
Then what is the opposite of Progress?