While I am not the best authority on this subject, I have some information. As a disclaimer, my cell phone is just that a cell phone. We use it to make phone calls and it costs us less than $20 USD a month.
My daughter and son are full blown cell phones and any other service a phone can do. They both have Metro PCS, It is inexpensive and no contract required.
I hope this helps.
Author of Jonas Watcher: The Case of the Running Bag at