IOS System Services > Time & Location uses excessive cellular data. Why? How to disable

Since iOS 11 update I noticed that my iPhone 6s started to drain cellular traffic very fast. Before, I was able to keep within 500 MB per month but now 1 GB is not enough.

I looked at the settings and noticed: the traffic is mostly drained by the system services. And not by the analytics but by the "Time & Location". Surprisingly, isn't it?

Here is the stats for last 10 days:

• 479 MB totally
• 308 MB for system services
• 261 MB for time & location
• 26.6 MB for push notifications

Here is some screenshots:

The first question is How the f.. they do it?

I'll not be a lier if I say that I'm paranoid about this. Look, I spent only 171 MB for messengers, maps, social networks and browsing. Why time and locations use so much traffic? 261 (two hundred and sixty-eight) MB!!! What are they downloading? A sound recorded 24/7? Or videos a videos of me?

Time is so simple to synchronise through the NTP. I can't believe that it can take more then a kilobyte. And there is no need to sync time more then once per month.

Location is simply provided by GPS. No cellular data required at all. But even if Apple want to track each my step it can't take more then 1 MB of text data per day.

So, it's a big mystery where is my traffic sucked in. Apple, please, collect your data using Wi-Fi.

And the second practical question is about how to fix this trouble

I noticed a similar question: Disable system services to save data

I have disabled some of items in Settings > Privacy > Location Services > System Services. I don't want to disable the other such as "Find My iPhone" because I think they are important.

I currently use a very simple solution: I'm turning of the cellular data when I don't need it and turn it on to check messages, for example. But if forget I can easily lose 50 MB for a night.