I have Charter cable, but they always contact me through a 888 number. Once when I was changing services and I took back one of the digital boxes to the store and got a receipt. I got a call from 571-364-0368, with "CHARTER" on the Caller ID, and this gravely voiced guy asked me if I needed to return any equipment? He knew precisely what I had. He said he could send someone to pick it up. I told him I already dropped it off.
Now I get calls, about once a week from this number, no one on the line. No answer when I try to call back. I watched a special on PBS about the Snowden leak, and he confirmed the old gossip, that intelligence agencies are indeed installing tracking tech into cable boxes and modems. So maybe this is the NSA trying to get their spygear back?
I live in Wisconsin.

You received a new 0:08 minutes voicemail message, on Friday, June 06, 2014 at 09:53:28 AM in mailbox 3523578688 from 5713640368.

I get it every day

I think this is a spoofed number, and not from Charter.  I received a call today, and the caller claimed his name was Glen Jackson.  He did know my last name, but since he called my commercial number, he could have obtained that from public sources.  Charter claims they did NOT make this call.  "Glen Jackson" hung up when I told him that our conversation was being recorded "for training purposes."  My guess is they are pretending to be Charter Communications, and if you are a Charter customer, you may be misled into giving up vital info and most of your bank account.  DO NOT FALL FOR THIS!

This number calls me 5-6 times a day claiming to be Charter and tells me that they can save me money by bundling my package. Well I already have their service and told them so and to quit calling. They however keep calling and it annoys my family to no end. They even call at 10 pm which by law is a telemarketing no-no. They need to quit. Do not give them any personal information. Beware!

I just got a call from 571-364-0368 Charter was on the caller ID but its not Charter Comm.. ,,I called charter comm and reported it and they said to call  the FCC,,they are trying to track down who ever this is doing this..they are calling this spoofing phone calls to people,,,FCC number is 1-888-225-5322  call and report this number or any number that is doing this.