Under Settings -> Cellular Data there is a nice break out of how much data each app has used. I expected this to allow me to identify which specific apps were using the most cellular data so I avoid overage fees. My carrier tells me how much data I have used, but only gives a general category of where my data is going, which is useless for this purpose.
However, I have only had the phone a couple of weeks, and it is claiming I have already used 17.4GB of data. However, per my carrier, I have actually used only 150MB. It is obviously counting WiFi in the cellular figures. But why? Am I looking at the wrong spot? Is there a bug in iOS? Something I am doing wrong? Something I need to enable? Could it be counting previous months on a different phone and need a reset somehow? Shouldn't it reset every month?