Actually, SW will give you a credit for the difference. You will need to use the credit within one year of the original booking date (not the travel date) unless you purchased a fully refundable fare. All you need to do is open two separate windows to the SW website. On the first window, with the new lower fare, type all of your info up to the point where payment is required. At this point, go to the second window , which you have opened to SW homepage and go to where it says cancel a flight. Cancel your original fare and immediately go back to the first page to rebook yourself on the same flight, using the credit you'll receive from your original cancellation......be sure to have your confirmation # handy because you will need it to rebook yourself using the credit. Then, after you've rebooked you'll be showing a credit for the difference which you will need to use within 12 months from the date you originally booked the trip.