There are times after you have booked a flight with Southwest Airlines that you need to change that flight for a different date or time. Luckily Southwest makes that process easy, as long as it's more than 24 hours from boarding time. All you need is the name under which the flight was booked and the confirmation number (which was sent to you via e-mail).
Go to the Southwest website, www.southwest.com. Click on "View or Change Your Flight".
Type in your name and confirmation number (which can be found at the very top of your confirmation e-mail) when prompted, and click "Go".
View the itinerary and make sure it is yours. Check the box next to each flight that you want to change, then click "Change Selected Trips". Please note that when you change reservations, it will change the flights for all of the passengers on the same itinerary and confirmation number as you. Also, your new flight might have a higher fare than your original flight and you will be responsible for the difference.
Choose the new details for the flight you are changing. You will be changing the flights in chronological order, so the outbound options will be shown first. You can change the city, the date or the time. Then make any changes that you'll need for the inbound flight as well, and click "Next Step - Choose Flights".
Click on the circle to select the new flights that you want, and then click "Next Step - New Price". Review the new fare, which may be higher than your original fare. If you're happy with the changes, click "Next Step - USA Reconcile".
Pay the difference with a credit card if your new flight is more expensive. If your new flight is less expensive, you will receive a credit for future use with Southwest. If the price remains the same, simply choose the method to receive your new confirmation.
Click "I Want to Make These Changes" to save.