Why has my Lumia 635 used a massive 850MB of data overnight for no known reason?

[Windows Central Question]

I generally only use 100MB of my monthly 1GB but over the weekend I received a SMA warning me that only 150MB remianed. Sure enough, Data Sense shows 850MB has gone to "Data To Restore." I have not touched a video, downloaded anything, back-ups are off, a compkete mystery. Any ideas please.

 

[pkcable]

Could the device have crashed and restored itself during the night?

 

[Jeremy Blankenship]

You are not the only one having this issue with the data sense.

To quote a post I put in another thread:

I was out shopping with the phone in my pocket doing "nothing" and when I got home I noticed a message on Data Sense app saying that I exceeded my usage amount. On the front of the app it is saying 7.43GB usage and when I swipe to the detail view on next screen it says 9.38GB usage. This when I have only used 243mb (180 being stupid auto updates turning phone on).

 

[karan25i]

My data sense does not show ant data usage.but i have problem with the mobile lumia 630wp pre10149.it takes about 40 mb data without using any apps.even in lock screen condition in 20to 30 min.

 

[lesnorman]

I have found out that One Drive has backed up a lot of photos I took on Saturday despite having the Back-ups setting set to WiFi only. I have now changed it to Never Upload and hope that has fixed the problem. Data Sense gives you the WiFi use for the various apps and they are innocent in this case. However it showed Data To restore as massive and that sent me looking at One Drive via the PC and sure enough there are all Saturday's photos. Thanks for all your advice, I have read every word and gone looking in the phone.

 

[pkcable]

If you don't 100% trust data sense, often you can check your data with your carrier, most have apps for this, OR it can be done at their website. I have Verizon and T-Mobile and they both offer this service via apps and on the web.