iPhone and cellular iPad come with data plans. That's the cost of being "always online". Since the days of unlimited data plans are largely behind us, most of us end up being bound to our carrier's tiered data plans and the overages that come with them. While overages may not be as expensive as they once were, they still cost extra money, and no one likes to pay more than they have to. If you find yourself pushing your data plan's limits, or actually going over it, there are some things you can do in order to monitor your data in the future. That way you can either better control your usage or change your data plan to one that better fits your needs.