Disabled mobile data but some data still transmitted I have expensive mobile data plan so I disabled mobile data in settings. But I still have a little amount of mobile data traffic every day that I paying for. (something near 100-1000 bytes, I inspected it in payment detalisation provided by operator)

I use home wifi for internet access so I need to disable only mobile data but not wifi.

I enabled restrict background data option but still have mobile traffic. (screen1)

In APN menu I can't delete/edit default APN supplied by mu operator. I created and selected fake APN as sugested in How can I disable mobile data completely? but still have mobile traffic. 

How can I (but not disable wifi)?

I suspect OS Android or Google services make this traffic. 
(screen2)

My phone is LG X style K200DS Android 6.0.1.
Install app like Glasswire and you can monitor your outgoing traffic. Or you can use firewall apps and try to disable the data on every app.