Am barraged by xFinity marketing emails - how can I stop them?

I am not a current xFinity customer, though I have an account (I have used xFinity on demand in the past when traveling).

I have been receiving CONSTANT xFinity marketing emails (18 in December alone), and have been trying for weeks to stop them. Clicking on the unsubscribe link at the bottom of an email does nothing. When I go to my communication preference page, it shows all my communication  is OFF.  

Please help! Thanks!