So I know that data and wifi are different and that data usage has a charge and wifi does not. However, when i look on my samsung at my data usage, it give me "mobile" and "wifi". The fact that there are two data usage sections makes me a little worried that there is actually a charge attached to wifi? I am told that there isn't but the fact that when i look at my data usage i see mobile and wifi makes me second guess what i previously thought. Sorry if it is a stupid question.