Southwest flight reservations can be change or cancel without causing charges up until 10 minutes before the timetable takeoff season of a flight. Regardless of whether you have check in, you can in any case get a movement credit as long as 10 minutes before departure. For details on How to Rebook Canceled Southwest Flight? Read below or Dial: +1 800 435 9792 or (OTA) +1-888-894-2072.