It's like this: Sprint has promised to cut your bill in half if you switch from Verizon or AT&T (though, notably, not T-Mobile).
The carrier will choose a plan that best matches your current deal on AT&T or Verizon, then offer it to you for half what you currently pay, while at the same time covering up to $350 of your cancellation fees for you.
You are, however, required to trade in your existing phone and buy a new one form Sprint, whether on a lease, in monthly installments using Sprint Easy Pay, or at full price up front.
You can sign up for a Sprint plan at half your current bill online or in stores starting December 5, and you'll keep that rate as long as your plan stays the same.
If there's a catch here, we can't find it.