I've just noticed that my data usage for Google Play Store this month is >350MB. I've got it set to update over WiFi only and background data is restricted, so I don't know where this has come from. I haven't been downloading any apps either. Does anyone know what could have caused this and more importantly how do I stop it? It's a Sony Xperia Z3 running 5.0.2. Thanks!
I recently had problems with my phone eating up an extra 4GB of my data plan in one month. Not fun.
First try, Settings -> Apps -> All, and reset cache for each Google Play Services, Google Play Store, and Google Services Framework. Restart the phone, and watch.
If that doesn't do the trick, try resetting the cache AND data for each of the three. Again, restart.