Charged for Movie I purchased through Apple

I purchased a movie through my Apple Account online, paid for the movie in my Apple Account, and watched the movie on my smart TV, not using the Flexstick Xfinity provided me with, which is connected to a different TV.

Why is Xfinity charging me 19.99?

The fact that Xfinity knows I watched a movie that was purchased through a different company and watched through wifi is quite bothersome and an invasion of privacy if you ask me. I own the movie on my Apple account.

Do they expect me to pay them 19.99 every time I watch a movie I purchased through Apple?

I am very upset and want the charge removed from my Xfinity account and an explanation as to how they thought they were entitled to see what I stream over their internet service through a different online service. Do they have access to everything I watch on Netflix, Hulu, Disney, etc because they provide the Internet service? Is that in small print somewhere that no one reads in the extra-long agreement?