iOS Shows Data Usage for Free – DataMan Pro Review

Go to Settings > Cellular and scroll to see how much data each app has used. Tap Reset Statistics, at the bottom, each time your data data plan renews. DataMan Pro turned out to be a waste. It's useless for people with pre-paid data (the norm outside the US), as it contemplates a regular monthly allotment. Ditto for post-paid customers (the norm in the US) with carryover data (lucky few) or add-ons like Verizon's PopData (a new offering, admittedly).
Review by paul4791 on DataMan Pro.