The number I called was 1-877-728-3184. Of course they may sing you a different tune, as they are apt to do.
I'd say don't worry about calling them about getting free basic. Just put a splitter on your line and run a cable to your TV and see what happens. You'll have to change your TV settings from "Antenna" to "Cable" to get all the channels if it works.
The "Expanded Basic" channels are 2-77, with a few in the 90's. It includes all the goodies like locals, ESPN's, Discovery, TLC, History Channel, etc. So getting those for a nice price is a good way to go.
It gets more complicated when you order digital cable. You have to pay monthly for the box, plus whatever packages you add to your deal. It never helps that Charter seems to add some charges on there just for fun. Things like "Service Charge" always amused me.