They say they have important information about my bill.  I have no idea who they are.  They're saying they are Comcast.  I don't owe my Comcast any money.

but who are they?

I received the same call. Thank God I googled it and this page came up. I will call comcast tomorrow

This number is a official sounding Comcast recording, How ever it is an Abbrev. of there recording when you call them. The message this number leaves will say it is regarding an important matter. It then says if you received a phone call press 1, a letter press 2, It also states you can pay your bill on the phone using your credit card.

This is NOT Comcast, It is someone trying to get you credit card information.

I called Comcast and let them know about the number, Comcast has confirmed this is not them.