Comcast is an ISP and Cable Television provider, with a terrible reputation. When I cancelled my service when them I had to mail the modem back to them. I did it UPS shipping with tracking, because I know not to trust them. They never-the-less claimed they did not receive it, and billed me for the device. Eventually - armed with the shipping confirmation - they acknowledged receipt of the package, but insisted that the box was empty and that I mailed them an empty box.

I forget the other details, but remember to never do business with Comcast or their subsidiaries / partners.