The title says it all: Under network settings in iOS 4 there are separate toggles for turning off roaming and turning off cellular data. What's the difference? If I'm abroad and want to avoid unwanted extravagant charges, I know to turn off roaming. Should I turn off cellular data as well? It seems redundant to me, but there must be a reason for two toggles. Also, with the cellular data switched off, is there still GPS positioning?