what are your dates...??
are you flying from buffalo, they now have two NON stops after september 15th
you can change the one you already have booked by going to the travel center and choosing "change air reservation"
you then have to put in your current confirmation number and name of the credit card holder on whose card the reservation was booked
when you click on "retrieve flight information" you will then have to click on the current flight you have booked as being the one you want to change and and then click on "change selected trips"
you will be then taken to a page which is similar to the original page you used to make your reservation
you put in your date ( same as you have now ), youre departure and arrival cities which will be the same also
click on "Go to next step--select new flight"
thenyou can actually see what is available before you have to make a decision about your change. ( if the same flight is available at a cheaper rate you can book it ) on this page you will see "go to next step -- new price" , which will probably price out the new flight at 30$ less and tell you there is ticketless refund being set aside for you ( have not gone this far yet since we have not changed any flights yet, so am just guessing that is what will occur )
...this way you keep your original confirmation number and you see what is there before you make the choice so the "premise about hoping the rate will be there" ( suggested by the agent you talked to ) would be mute....the difference is given to you as a ticketless credit good for future travel
others have posted here that they have been able to get "credit card" refunds for the difference by calling a SWA number in dallas
but, in your case, since you do not seem to have booked your return flight ( the good rate is only good for flights until september 30 ) you coulld book that using the "ticketless funds" you get if and when you can change your first leg of the trip
hope this helps....