O2 unusual decline in data use?

[Ahez]

My O2 data seems to decline very quickly despite moderate use. I used to be able to survive on 10gb a month, then suddenly I needed 20gb despite the same level
Of use. Recently 20gb was not enough and I upgraded to 40GB. I’ve been at home
All during April and using WIFI so data Shouldn’t be in use. However
3 weeks into using the 40GB I run out of data. I don’t stream videos, use a lot of social media or use it as a personal hotspot, only for browsing internet. I downloaded an app
To monitor data use and already one day in the app says I’ve only used 960mb whereas the official O2 billing app states I have used approx 2.4GB.
Has anyone else had this experience? I am going to bring this to the regulator once I have tracked the use for the month and shown a pattern

[pgn]

Lots of things can do this, especially if you use an iPhone, @Ahez.

O2 provide a few tips here, just before you escalate to any official channel:

https://www.o2.co.uk/help/account-and-billing/understanding-data

[jonsie]

Switch off mobile data altogether when on wifi

Also look in the wifi settings on the phone to make sure there is no wifi assist settings which will cause background apps to use data.