On the iPhone go to the "Phone" then go to keypad.
Type *646# (*MIN#) to see minutes used, Rollover Min, Unlimited/n&w min.
Type *3282# (*DATA#) to see how much data sent/received...don't bother since its unlimited it wont really tell you.
Type *225# (*BAL#) to see how much you bill/balance will be/is.
To see the data, go to Settings, Usage...then scroll down. Under Cellular Network Data it will show you Sent/Received.
Off topic.... I just checked mine, and in 3 days i sent 54.4MB and Received 2.5GB. LOL!