If you are looking to sell or trade in a Sprint-branded iPhone, 1. Major Carriers & Manufacturers (Best for Upgrades)

These "buyback" sites are often the best route if you want cash instead of store credit. They refurbish the devices for resale. Cell Phone Trade-In: Check Trade-In Value, Deals & More

and Verizon : These carriers often have aggressive "any carrier, any condition" promotions to lure customers away from T-Mobile. 2. Specialist Trade-In Sites (Best for Cash)