"System Services" uses cellular data EVEN AFTER turning off Cellular Data

Hi everyone,

I'm traveling abroad and I have my work phone to cover my need for data, calls, and most texts.

However I still need my personal phone for just one thing -- receiving one-time codes when I needed to log on to my various accounts. In order to avoid paying for roaming charges (receiving texts is free for my cellular plan), I turned OFF cellular data (which apparently also turned off data roaming), and "reset current period" so all cellular data usage was reset to zero.

Today I found out "System Services", and only it, used 1.0KB of data, and quite obviously roaming data. I checked again and yes, my "Cellular Data" toggle switch is indeed set at OFF.

I clicked on "System Services - 1.0KB" and then found only "Networking", but nothing else, used that whole 1.0KB.

Anyone has any idea what's going on here?

I was expecting when I turned off Cellular Data I should see absolutely 0.0KB of cellular data usage.

I'm using a pay-per-use plan for data roaming and it's $2/MB. For this 1.0KB it isn't an astronomical amount of money but how can I make sure, while with Cellular Data is turned to OFF, iOS won't somehow find a workaround and use more data for this "System Services", and next time, for 100MB?

Thank you!