That is correct there is no way of knowing who is using the service from a caller ID perspective.
They are coming over a phone line, but DSL runs at a different frequency then your telephone does.
Even though they are on the same wire, they are seperated within so you will not have a voice call go through to the ISP circuit path and vice versa if that makes sense.
The only way you will know who is using your service, is by the username they enter in when connecting if you do PPP authentication.
Daniel
