T-Mobile and Sprint are fighting to buy back your old smartphones

A day before the launch of Apple’s iPhone 6, T-Mobile and Sprint unveiled their device trade-in programs to lure in subscribers who want to get their hands on the latest iPhones. In the past few weeks, the two companies have gone head-to-head in an aim to gain subscribers, by giving away switching incentives, slashing prices, offering discounts on phones, and upping data usage on mobile data plans.