Urgent!!! How do I find the phone number of the modem connected to my router?

I need to find the phone numbers of the modems that are connected to my routers.  AT&T is requesting this, and I need to get back to them asap, any help would be appreciated.
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Apparently you don't have it documented so you'll have to physically trace the phone line from the router to the wall jack.  Hopefully from that point you can match it to the phone number or continue to trace the cable to your PBX or your providers network interface.  The phone number should be documented on their equipment.
your modem is plugged into a phone line, yes?  if so, get an old phone and plug it into each wall jack that is being used by the modems for your routers, and call your cell phone or some line that has caller ID.

might be easier if your in front of the modem, and just unplug the phone cable from the modem and insert into a normal phone & then do your call to cell phone or other line that has caller ID.

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