With the new iPhone making its debut later and other phones coming out in the next few months, you're probably already looking for the best way to trade in your old device for a new one. Sprint and T-Mobile both want your business really badly, it seems, so now they're trying to one-up each others' -- and everyone else's -- buyback programs. While the Now Network has long paid up to $300 for old gadgets, the company will now start matching any higher trade-in price you get from the other three major carriers, in an effort to offer the best deal possible. But Big Magenta won't go down without a fight: in case you get a better buyback pricing from another carrier, the company will not only match it, but also add $50 on top of the total amount to make the deal sweeter.