Brian is looking beyond the "big three" of cellphone carriers and wants to know which one of the smaller mobile carriers are best. Leo says that most of the smaller carriers, known as "mobile virtual network operators" (MVNOs), buy their network service at a discount rate from the big three, often times Sprint, and then resell it. And it's often a better value than the big three. Straight Talk Wireless from Walmart, for instance, is one such MVNO. Which one is best will depend on which of the big three's are best in Brian's area.