Since my phone plan isn't very...well enough going "over" on data and the like isn't a good idea. Wifi I know will lessen the horror phone plans can inflict but how can you tell when an app or whatever is using the cell signal or the wifi? If I turn on airplane mode I turn everything "off" to the outside world...right? Is it possible to "turn off" or whatever you call it the phone service while using it in a wifi area (manually)?