Software Updates using a lot of Mobile Data

1. Is this your corporate iPhone? Then please contact the system administrator of your corporate
2. If it is your personal device, in that case, do you have any profile installed by your corporate/organisation/enterprise/School Management?
   1. Erase the profile added by you If you have installed a profile on your own --> Install or remove configuration profiles on iPhone - Apple ...
   2. Or please contact the system administrator of the organisation who provided the profile to you

I don't think the data shown is for the day. It is for the period. Ask your Carrier for the period-wise data usage.

Settings > Mobile Data [Do you see Current Period?? ]

Scroll down to the bottom to what this current period is.

• If you're using an Exchange ActiveSync account, it may continue to use mobile data even if you've turned it off for Mail and Calendar. To see the mobile data usage of your Exchange ActiveSync account, go to Settings > Mobile Data > System Services.

How sure are you that the 82,39MB of mobile data usage was after the mobile data was disabled by you on your device? Maybe the data consumption got refreshed by iPhone. What you see on iPhone mobile data usage is only indicative and for reference. What your Carrier charges you may not match with this data always.

Contact your service provider to get the most accurate mobile data usage from a current period.