You can stop playing multiplayer, that'll stop using bandwidth since you're playing on a metered connection.
FPS games only have to tell the other players maybe what you look like, what kind of weapons you're using, what you're doing at the moment, and if they've been shot.
Crafting survival teraforming games like Valheim have to send terrain changes, building and craftable changes as well as much more, and that's a lot more data. Learn this so you can better allocate your bandwidth usage.