As competition increasingly heats up among wireless providers, offering an unlimited data plan has basically become a necessity. But just how "unlimited" are these plans actually?

We took a look at the fine print at the one line plans offered by Verizon (VZ - Get Report) , T-Mobile (TMUS - Get Report) , Sprint (S - Get Report) and AT&T (T - Get Report) . While you'll always be able to call mom (sorry), you may encounter slower speeds after a certain amount of data usage when your network gets congested. 

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Editors' pick: Originally published July 25.