It is absolutely possible and simply requires you to be insistent, as in "I want stand alone broadband!" Decide which speed you need: https://www.dslreports.com/faq/15643. and just don't take no for an answer.
No one can make you buy services that you neither want or need, not even Comcast
I suddenly remember that when I did it in 2011 I had to threaten to leave, but everyone is cutting the cord nowadays so I think it's not such a big a deal and won't require any dramatics. I don't game or have more than a few movies/shows streaming at the same time so I get by just fine with Performance Starter (Your Mileage May Differ).
Hello, and thank you for reaching out to us. I would be happy to assist you from here. Can you verify your account information with me? I would need your phone number, full name, and service address. You can private message me by clicking my name and clicking private message.