FreedomPop is quite an interesting service. It offers free, albeit limited, smartphone plans. They have now added iPhone 5 to their list of offerings. You can get a refurbished iPhone 5 for $349 and pair it with a free plan that offers 200 voice minutes and 500 text messages. You can get unlimited voice and text in addition to Voice-mail for as low as $4.58 a month (two year plan).
The service allows you to buy additional voice minutes and texts. You can also pick Android phones. The iPhone 5 deal is not the greatest in and of itself, but the free voice plan is worth checking out.