Yes — with Southwest Airlines you can change your flight, but the rules depend on the fare and timing:
You may make a change up to 10 minutes before departure.
For most fares there is no change fee, but if the new flight costs more you’ll need to pay the difference; if it costs less you’ll receive travel credit.
Some lowest-fare categories may have more limited change flexibility.
Always check your specific fare type and flight rules when making changes.