How to stop facebook from auto downloading videos on both my PC and iPhone?

I stopped the "autoplay" feature, but the thing is facebook still downloads the videos and eats alot of bandwidth.
I know that because when I click on a video even if i'm not connected to a network it plays without buffering, and whenever i open facebook it slows down my internet drammatically

Added (1). the thing is these videos start downloading even if i don't click on them

There's No Way To Stop That When A Video Opens Its Gonna Download Either Way