Can apps/services use mobile data even if it's disabled?

[AC Question]

Hi all,

I have the following problem. I'm on a business trip to the USA and phone charges while roaming are steep. That's why I made sure to disable mobile data in Settings to avoid paying for traffic. However, I got charged USD 30 anyway; my carrier explained to me that I've used mobile data on several different days and that it's probably due to some background tasks.

I find that hard to believe though. As I said, mobile data has been disabled globally the entire time and I see 0 bytes of mobile traffic since I came to the US.

For completeness, my phone is Nexus 6P with Android 7.1.2, August security patches installed.

Can someone answer the following questions? I really want to get to the bottom of this.

1. Can mobile data be used by some apps/services even if cellular data is globally disabled in settings?
2. If so, how can I find out which apps/services exactly have the ability to do this? I was browsing through the settings and in Settings -> Apps -> Configure Apps -> Special Access I see a section called "Unrestricted data access". Is that it? I had two apps with this enabled, one was Carrier Services and the other probably was Google Play services ( I don't remember, I disabled both).
3. If some apps/services were using cellular data, why isn't this reflected in the Data usage statistics? Some data got transfered back and forth and I'm seeing 0 B, which is apparently not true.
4. Where can I see how much data has been used in the background?

Thanks in advance!

 

[lucianus_luciferus]

if you disabled the data then no app can go online even in the background. tell your carrier you are not going to pay that unless they can prove it
settings, connections, data usage, mobile data usage

 

[L0n3N1nja]

If mobile data is disabled, it should be impossible for anything to use data.

 

[Filip Kolev]

So, I requested detailed info about the data used and my carrier provided it.

Again, my question remains. How is this possible? Should I contact at&t as well, since they're after all the ones who are charging me for this traffic?

 

[lucianus_luciferus]

go for it

 

[Mike Dee]

So, I requested detailed info about the data used and my carrier provided it.

Again, my question remains. How is this possible? Should I contact at&t as well, since they're after all the ones who are charging me for this traffic?

It's not possible and yes you should contact your carrier.