Disclosure first: I wrote this.

My bundle kept running out before the month did and the phone only ever showed me a total. Android's own per-app data screen defaults its date range to the calendar month instead of the billing cycle, so the numbers never matched what I'd actually been charged for. When I finally pulled per-app figures out of NetworkStatsManager the biggest consumer that month wasn't video or anything social. It was a tile-matching puzzle game, almost all of it background, while I wasn't playing it.

So it ranks every app by what it used this cycle, counts foreground and background separately, and lets you block apps per network, which means something can be dead on mobile data and work fine on Wi-Fi. Play Services, your dialler and your SMS app are protected, because blocking the wrong thing silences every notification on the phone and it takes a while to work out why. I did that to myself before I understood it.

No INTERNET permission at all, so it can't send anything anywhere. Don't take that from me, the permission list on the Play page is extracted from the uploaded build.

GPL-3.0, free, no ads, no purchases, Android 7 and up. One limitation worth saying out loud: it holds the VPN slot, so you can't run it alongside an actual VPN.

Source: https://github.com/anubisproductions/data-saver-usage-blocker Play: https://play.google.com/store/apps/details?id=com.anubisproductions.datagate