Excessive mobile data (cellular data) usage by Documents & Sync
I've had a problem for the last 3 or 4 days of my iPhone using excessive amounts of mobile data.
Typically in an entire month I use about 3GB of data. In the last 4 days I've used over 2GB despite spending most of the time in locations with WiFi.
Once I realised something was up (when I had to buy 2x 1GB data upgrades within 72hrs). I started looking for a cause using the data given under Settings > Mobile Data (Cellular Data).
Tried a couple things:
1). Under Settings > iTunes & App Stores "use mobile data" was set to On.
This was odd, I'm pretty certain last time I checked this was set to off. Anyway, I changed it back to off.
Under Mobile Data > System Services I could see the data used by iTunes had dropped back. This helped reduce data usage but hasn't solved the problem.
2). Under Settings > iCloud > iCloud Drive "use mobile data" was set to On.
Didn't know about this one, but discovered it googling for a solution. I changed it to off. Made very little difference.
After making these changes I switched Mobile Data back on. I was still seeing massive data usage, about 50MB in 30 minutes.
When I checked back in Mobile Data > System Services by far the biggest user of data is listed as "Documents & Sync". I don't know what this does.
I signed-out of my iCloud on the phone. This did seam to help but I couldn't leave things this way for long as I was missing my calendar and contacts so I signed back in and switched on all my iCloud services (except email) again.
So right now I have mobile data switched off completely. I'm only able to use my phone on WiFi, so it's basically a super expensive iPod Touch.
I really need some help with this, I'm hoping somebody can please point me at a solution or at least explain what might be using data labeled as "Documents & Sync".
If I can't get to the bottom of this one I'll have to switch to another phone, my carrier here in New Zealand don't offer unlimited plans :-(
Some details on my phone and settings:
- iPhone 6 running iOS 9.2.1 (13D20)
- Phone has 128GB storage with about 10GB free space
- iCloud I use for everything except email and document storage
- I have iTunes Match and Apple Music subscriptions
- iCloud Photo Library is switched on
- Everything I can find with a setting for it except for Apple Music is set to only use data over WiFi
iPhone 6, iOS 9.2.1, 128GB