For everyone you refer successfully, you can get $150 Noble Cash!
Every Noble Member gets a unique code to share. If someone signs up with that code and transfers an existing phone number to Noble, they'll get their first month for free! You'll then get $150 in Noble Cash once they've stayed a Member for 3 months. There's no limit to the number of people you can refer (and no limit to the amount of Noble Cash you can earn through referrals).
Once you've activated your service, you can get your unique code and track your referrals in your Noble account dashboard: https://noblemobile.com/dashboard/referrals.