The latest Facebook iOS app includes auto play for videos. That means is that videos people post to your Facebook page will start to play automatically, only without sound. This could spell problems if you have a usage quota that you have to stay under. While you can’t completely turn this new feature off, you can disable it to save your usage amounts.
To disable auto play for videos on Facebook for your iPhone, open the Settings app and scroll down until you see Facebook and then tap on that. After you have tapped on Facebook, tap on Setting and tap the On/Off toggle next to “Auto-play on WiFi only” under the Video section to turn it on. This way the videos on your Facebook newsfeed will only play automatically if you are on Wi-Fi so it won’t use up your data minutes.