Preventing my apps from using data?

[skan]

Hello.
Since a few weeks ago some app on the mobile is wasting my 4G data, and I have to pay for it.
Maybe is some kind of automatic update.
How can I prevent this problem and allow the apps to use the Internet only when connected through the WiFi?

 

[skan]

Come on now, it's basic stuff this.

Settings - Installed apps - "the specific app" - Permissions

or

"Security" app - Data - Restrict data

Strangely all options there are OK, and apps say they haven't used data but my phone provider has charged me as if I had used 4GB.

 

[cobben]

I assume you have checked which apps might be guilty in:
Settings/Data usage

Google has an app for this, have never tried it:

Datally: data saving app by Google

Datally: data saving app by Google - Apps on Google Play

Datally is a smart app by Google that helps you save, manage, and share your mobile data. On average, people save 21 percent of their mobile data—that’s like using data Monday to Thursday, and having Friday covered by Datally. SAVE DATA More data for the apps you care about. ● DATA SAVER -...

play.google.com

If this doesn't find the problem, you can install the firewall app Netguard and turn off internet access selectively for everything, also system apps.

 

[skan]

I assume you have checked which apps might be guilty in:
Settings/Data usage

Google has an app for this, have never tried it:

Datally: data saving app by Google

Datally: data saving app by Google - Apps on Google Play

Datally is a smart app by Google that helps you save, manage, and share your mobile data. On average, people save 21 percent of their mobile data—that’s like using data Monday to Thursday, and having Friday covered by Datally. SAVE DATA More data for the apps you care about. ● DATA SAVER -...

play.google.com

If this doesn't find the problem, you can install the firewall app Netguard and turn off internet access selectively for everything, also system apps.

OK, thanks.

Before reading your answer I installed Glasswire, that monitors data traffic and tells you how much is used by each app, if I can't solve the problem I'll try Netguard.
I've just started to use it but I've seen that even the gmail app (I have 5 accounts) use a non-negligible amount of data every time it syncs. Also the system itself uses some.

 

[cobben]

OK, thanks.

Before reading your answer I installed Glasswire, that monitors data traffic and tells you how much is used by each app, if I can't solve the problem I'll try Netguard.
I've just started to use it but I've seen that even the gmail app (I have 5 accounts) use a non-negligible amount of data every time it syncs. Also the system itself uses some.

Yes, mail can use a lot of data (and battery) if you sync several accounts, especially ones with lots of mail and far back in time.

Otherwise cloud backups of various things can use enormous amounts of data, including Mi cloud backup & sync.