CALLER ID?

[Neil Haller]

That means your office is served by a PBX.  With PBX service you
have some incoming trunks and outgoing trunks (technically they
are lines, but let's ignore that).  The number of lines in your
company is much greater than the number of incoming and outgoing
trunks.

The ANI data is the line id of your outgoing trunk. Incoming calls
must pass your extension id and connect through an incoming trunk.

Neil