What is a Good Low-cost Mobile Phone Service?

Jenna is a veteran and she doesn't use her tablet much. She's thinking of selling her tablet and going with a cheap phone and a cheap internet plan. Leo says that's a good plan, especially if she goes with a low-cost data plan with WiFi.  T-Mobile has a plan for those over $50. It's pretty cheap. But there's also MINT Mobile, an MVNO that resells phone service from T-Mobile. $15 a month or less, and she can bring her own phone.