I've got a new iPhone SE with all settings transferred from iPhone 5.
I noticed that once a day, at around lunchtime, the phone heats up for around an hour or two, eats half of the battery and presumably also sends or receives a lot of data over 3G because every few days I get a SMS from my provider alerting me that I used 80% of my prepaid 1GB data. The phone is not on charger when this happens (I usually it recharge overnight).
This wasn't happening on the old iPhone 5 - there the 1GB of data lasted for a month or more and battery on light use easily for 2 days.
I doubt it's the iCloud backup - it should only run over WiFi and while the phone is in charges (or so it says at least). I also have the background refresh turned off, email on manual fetch, firmware 9.3.3 (latest as of now), etc. All I could think of that could trigger some background activity was disabled. Yet still it happens every day.
What's going on here? Thanks!