Southwest Airlines has one of the most customer-friendly cancellation policies in the airline industry. You can cancel any flight up to 10 minutes before departure without paying a fee. If you booked a “Wanna Get Away” fare, you’ll receive a travel credit for future flights. For “Anytime” and “Business Select” fares, you can get a full refund to your original payment method.
Source: https://www.devex.com/people/can-i-cancel-a-southwest-flight-without-penalty-policy-2028268
