My favorite thing about Southwest is the ability to change or cancel flights with no fees or penalties.
This allows you the opportunity to capitalize when Southwest lowers fares – simply book at the lower price and cancel the original flight.
The challenge always was looking up your original flight and comparing that to the current prices. Southwest just made the process easier.
Now when you log into your account, click on one of your trips, and then choose “Change”. Note that on the next screen your flight will show up, but it says “UNSELECTED”.

Click on the flight and it now shows as “SELECTED”.

Update your departure and arrival cities, and your date of travel (or keep the cities and dates of your current reservation. Click “Select New Flights” in the yellow box, and you get the following screen.

Note that instead of the overall price of each ticket, it now shows the difference between what you paid and the cost to change the ticket. The “+” sign means the ticket costs more, so look for the “-“ sign to see if any of the flights are now cheaper than your original flight.
Good luck. I hope you find some cheaper flights more easily.