Unexplained use of my internet quota

[medosoft]

I have been using my phone as a hotspot for my PC for two weeks now due to some problems with my landline internet connection, it was going fine till yesterday when I started noticing a strangely high use of my quota

For example, this morning I had reset the internet usage monitor on my phone, and for 3 hours I did not use the internet except for some light browsing every now and again (like Google Translate, etc.), However, when I checked my phone I found out that it has recorded over 1GB of usage under the “Hotspot” item, my phone carrier had registered a similar usage as well, which does not make any sense.

More importantly, I checked the firewall on Kaspersky Internet Security installed on my PC, and it had only recorded a total of 30MB activity that day.
For your information, I am limiting my hotspot to USB-mode, so there should not be any risk of getting my hotspot hacked by an outsider. In addition, I checked, and no applications are being updated in the background, and even if there was, it should have been picked up by the firewall.
Moreover, the problem persisted over 2 different phone carriers on 2 different devices; one is iPhone 4S, and the other is Samsung Tab 3, so the problem has nothing to do with the phone or the carrier, it is in my PC.

Does anyone have any possible explanation to this problem and, more importantly, any idea how to solve it?

My PC specs are:
Processor: Intel Core i7 3770
MB: Gigabyte GA-H77M-D3H
VGA: AMD Radeon HD 6750
HDD: WDC WD10EZRX 1TB
RAM: 8GB DDR3
OS: Windows 10 Pro

I appreciate your help guys.

 

[PsyKhiqZero]

I hear windows 10 updates are shared over user's bandwidth. It could be the extra data your seeing is the updates going out to the net.
http://www.howtogeek.com/224981/how-to-stop-windows-10-from-uploading-updates-to-other-pcs-over-the-internet/?PageSpeed=noscript

 

[smorizio]

use a malware scan and hitmanpro scan see if it malware sending ping packets. also check to see what on in msconfig when windows starts things like java updater and apple aps and nvidia driver updater can send packets every few min that can add up to a lot of data.