How to prevent any data connections/transmissions over mobile phone provider
I have a Sony Xperia Z1 compact D5503 Build 14.6.A.1.236.
I do not want to have any network traffic(TCP/IP) going via mobile network 2G, 3G and/or 4G. For this I deactivated whole month January 2016 "Mobile data transmission" and restricted completely all "background data transmissions" in Android.
Despite this my mobile phone provider has listed several connections and transmissions of data 20KB each for January 2016.
How to prevent any data transmissions over mobile 2G/3G/4G?
How to know what caused this traffic?