It's Charter Communications Sales. They are the provider in my area. I get snail mail junk at least once a week too. I'm not a customer because they are known to have terrible service. Pretty much everyone I know in the area is with AT&T U-verse or has a dish. It's not surprising Charter is spending zillions on advertising, junk mail and robocalls.
I got a call from this number; they did not leave a message. When i tried to call back, my phone service provider said I do not have enough credit to return the call. So I called a friend and it was fine. I don't know what is going on, but this number does not want to be called.