I'm at an office with one phone line and five people. I'd like to have
a phone or an add-on device that picks up the incoming call and plays
the recorded message "To talk with John, press 1, to talk with Jane,
press 2, ...." According to the selection, it plays distinctive ring
tone or a message recorded by each person so that the right person
picks up the phone.

I need this function to avoid Jane taking a call intended for John and
transfering. I want to know which device can do this and the price
(should be less than $100).

This might be useful:

http://www.cwol.com/rm2.htm

This doesn't do what I need and furthermore, it requires a paid
service from a telephone company. Any other idea?