Sprint will give you a $200 prepaid card for each line you switch
The deal works for existing customers also. If you are a Sprint subscriber and switch a number from another carrier to an existing account, you can get $200, or $100 for each new line added to your account (unless it's a 50% off plan).
Getting on board is easy. Turn in an eligible phone in the Sprint store, register online within 30 days of activation, and receive your prepaid card within 6 weeks.