....check you phone settings to confirm that "Data Assist" is turned off. Just do a Google search if you need more details of what it is and what it does.
I'm from Pakistan and As soon as I landed and turned my phone (6S) on, I got a notification from my carrier saying that I was using data and that I'd be charged a daily fee (something like $10 for 100mb) or I could buy an international data package.
Immediately I checked to see if cellular data roaming was on, but it wasn't. Just to make sure, I also turned "Cellular Data" off altogether.
Now I received my bill and they're charging me as if I had used data everyday during my trip. When I check usage details it's ridiculous, with several lines showing values as low as 84 bytes and the highest amount being 110Kb. The total usage for the 10 days is 1969Kb, but my phone showed 0 bytes.
Does anyone know what could be behind this? I have no idea what could use 84 bytes of data other than some network check or something. I'm trying to dispute the charges with my carrier, and I'd like to know if maybe they're the one at fault?
Also, I just want to mention that I traveled abroad a lot for work and never had this problem before, but this is the first time that I was using the 6S + iOS10 + this carrier, so I guess it doesn't really mean anything.