Unless they are fully refundable fares, you will be issued a credit toward another flight within one year of your original BOOKING date.
If they were booked on points, all points will go back into your account.
From their website :
If you are not planning to travel on any portion of your itinerary, please cancel or change your reservation at least 10 minutes prior to scheduled departure of the flight. Customers who fail to cancel or change their reservations at least 10 minutes prior to scheduled departure or fail to board their flight(s) on any Wanna Get Away or DING! fare segment are subject to our No Show Policy. Additionally, the entire reservation including any remaining flights on the ticketed itinerary will also be cancelled and all funds from the No Show reservation will be forfeited and may not be used or applied toward future ticket purchases. Reservations booked using Rewards points, Companion passes, and Reward seats are not included in this policy.