How does a DSL modem know which ISP to connect to?

I am terminating my contract with my old ISP, however, because I've already paid my account till the end of the month, this connection is still active. I have also signed up with a new ISP who mailed me with a new modem preconfigured with all the settings necessary to connect.

After I hooked up the new modem, it negotiates the PPP successfully, but fails at user/pass authentication. I called up the new ISP and was informed that they couldn't even see my modem's attempts to connect, which led me to think that the new modem is somehow still trying to connect to my old ISP. The call was logged as a fault, but I'd like to be a little more informed on the problem myself.

How does a modem know which ISP to connect to? Is there a setting on it that uniquely identifies each ISP? Or is there something that needs to be done on the DSL/POTS cabinet down the road?

Solution 1:

It is up to your phone company to patch your line to the new ISP's DSLAM. When you signed up with the new ISP - they placed the transfer order with your local phone company and the phone company scheduled a date when the switch would happen. Your new ISP should be able to look up the date for you. The delivery of the new modem may happen before the switch - it does not mean that it would work right away. If the switch date already passed then your new ISP should open a ticket with the phone company. Otherwise you should just wait for the date.