Disable video on mobile

I'm not gonna put effort on a big post. I'm gonna make this easy to understand and to upvote:

I have my phone in my pocket. Screen locked. I'm talking with two friends.

Suddenly they turn on their screens to look at each other. Now I'm lagging because it's using all of my bandwidth.

I'm. Not. Using. My screen.

This is beyond nonsensical. Please give us an option to disable the video on mobile.