Samsung
Turn Automatic App Updates On or Off auf Samsung
Automatic app updates run through the Google Play Store, not through Samsung's own system settings. That is why searching in Settings on the phone itself will not get you there.
The setting controls whether apps update over any connection, only over Wi-Fi, or not at all. If it is set to update over any network, background downloads can use mobile data without any warning, which explains sudden data usage spikes.
Turning updates off completely stops security patches and bug fixes from arriving automatically. That is fine for apps you rarely open, but risky for banking apps or anything handling sensitive data, since known issues stay unpatched until you update manually.
Where to change it
Open Play Store ➔ Google account ➔ Settings ➔ Network preferences ➔ Auto-update apps. Pick the option you want and confirm with Done.
The Play Store offers three choices here: update over any network, update only over Wi-Fi, or do not auto-update apps at all. Choosing Wi-Fi only is usually the safest middle ground, since it keeps apps current without touching your mobile data plan.

