I've been having the same problem. Finally called it back, had to sit on hold for a few minutes, and expressed that I do not want to be called. I was removed from the list no questions asked. Easy enough, but really not worth my time, Charter.
We have internet and cable through Charter. They suck on a massive scale. For about a year and a half they were calling and calling, leaving no messages. Finally I went to their website and opted out of contact by phone. That worked - until about a week ago when I called them to upgrade our internet service and get rid of their leased outdated gateway/router. I bought my own newer much better one because I was sick of their slow speeds and constant dropping.
Now they are calling again! If they are trying to sell us a bundle option or whatever, they do not offer any of that in our area. We have no other cable/internet options in our town. EVERYBODY here hates them. I avoid calling them at all costs because then they start on their calling campaign again...argh!
That number is Charter. I phoned my local office and they put me on their no call list. Charter will no longer give me calls me like that. They will only call in response to my specific calls or to let me know I am behind on my bill.