Data usage shows it is using data even when I turned off any data usage

I have already seen a Post with this subject but this person found out it was her hsuband in my case Im still not knowing the reason why my iphone 6 uses data even when I turned off any possible way of using data, turning all apps off, erasing icloud, everything, for example, it says 6.1MB and then I check it back again in an hour and incredibly arises to 6.3MB or so... Should I know something about sync apps that could be using data?