Stop background data usage in Windows

First search out which processes are eating up your data in background.
a. Type Resource Monitor in search bar.

b. Go to network tab and look out for the process which are downloading/uploading.

c. Once you identify the process, right click and kill the process tree.

d. If that process keeps on starting up on system startup then you need to remove it from startup. So do following steps.
1. Download CCleaner : CCleaner 5.10.5373
2. Go to Tools -> Startup .
3. Right click on process and select disable.

done