Why Do I See Cellular Data Usage, Even Though I Have My iPhone Set To Cellular Data Off?

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Why do I see cellular data usage, even when I have my iPhone SE2020 set with Cellular Data Off? (I also have Cellular Roaming within that setting turned off).

I recently switched from Rogers prepaid plan to Chatr. I did not have any data with Rogers prepaid, but now have cellular data with Chatr (30GB for the year, with my yearly plan).

I therefore did a lot of research on how to minimize and eliminate data use. (I have learned to live without data, using WiFi for everything in the past, but now that I have it, I will use it for GPS traffic and occasional internet if WiFi is not available.)

1. I have cellular data turned off unless I wish to access it.
2. I have background app refresh turned off for all but a couple of apps.
3. I have WiFi assist turned off.
4. I have notifications turned off for most of my apps.
5. I have low data mode turned on.
6. I have set the app store to not use cellular data.
7. I have looked to see which apps use cellular data.
8. My phone has been at home connected to WiFi when these usages occur.

When I look at my iPhone, I can see that “System Services” have used some small amount of data each day. They are Push Notifications, and a few others.

I accessed my Chatr account and looked at my usage and every day since I migrated to Chatr, a small amount of data is used several times a day. It’s always a small amount 0.01 MB, 0.02 MB, even 0.00 MB, but it shows up there and on my cell phone under Cellular in KB.

My question again, since I have Cellular data off, why/how are these “System Services” accessing data? They never did this when I was with Rogers prepaid and I didn’t have cellular data, so why are they using it now despite data off? 

P.S. I searched the web for this topic, however, I never found a good answer, even though this question has been asked several times...  My guess is that System Services simply ignores the Cellular Data Off setting, but I don't know why, especially since my iPhone is connected to WiFi when these data usages occur.

[TwitchyPuppy]

Do you have any location services enabled?

[LordDrakkon · Accepted solution]

What most don't realize, is that today's devices are never truly disconnected. Even when you think the device is turned off, it isn't. There are a lot of systems apps and services as well as just terrible apps that can and do enable data without any way the user can see or stop to do whatever it is the app needs to do. Find My Phone is probably the best example of a good thing that does this. Facebook, WhatsApp, and all other social media apps are perfectly examples of bad things that do this to mine your data. That is how these devices and apps are designed! Convenient for the user, but money making for the phone manufacturer, carrier, app developers, OS developers, etc.

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@LordDrakkon : Thanks for the reply. In my web searches, I found that certain apps do bypass certain settings, as we have discussed in the various roaming threads.  I don't use Facebook or Whatspp, so on my phone the only data usage is coming from "System Services" which I can see on the phone's cellular page.  It should use WiFi when I'm connected to WiFi, but it doesn't.

If I could get System Services to stop using data, then I wouldn't have to worry about having my phone in airplane mode when travelling to a foreign country, but it appears that's impossible, as we have discussed in roaming.  It was obviously not using data when I was on Rogers prepaid since I had no data, so it was weird that it now uses it when I have a WiFi connection and WiFi assist is off, all other settings are "correct", etc.

@TwitchyPuppy : Thanks for your question. As we discussed in this forum, location services are one of the items that can trigger roaming, but again, I could use location services on Rogers prepaid without data (when connected to WiFi) and it worked just fine.  I have location turned on on my Weather app when I travel, so that I can get notices and was able to get notices through WiFi.  So far my Weather app has not accessed data.

Yesterday I turned on cellular data to experiment with Google maps for about 10 minutes.  I could then see that Google maps had used data and also accessed location through data (can see location utilized under System Settings). Google maps used about 3 MB of data during that time.

Again, people should be complaining about certain apps using this data usage since it should not be allowed to happen.  It uses small amounts of data when in the home country and can trigger huge roaming charges when abroad.  The complaints should be directed at Facebook, Whatsapp, Instagram, Apple itself, etc.

Here's a good link on the topic:

https://www.cnet.com/tech/mobile/apps-that-use-the-most-data/

For most of these apps you're supposed to be able to turn off cellular data, however, some of them don't have that option or override your settings and use small amounts of data anyway.  Disgusting.

I guess the majority of people are so addicted to their phones that they pay and pay.