I'm sorry...I don't have a code to share, but I do have some useful information.
We had already purchased flights from Buffalo to Orlando at $89.00 per person one way, for a total of $812. for 4 of us all in. The price is down to $69.00 each way, and if I used the $25.00 code, it went down to $56.50 each way per person..or a total of $572 all in for 4. We would have a credit of about $240.
Now...how would I go about doing this??? I read some of these forums, and found out about the flight change feature. So I could 'change' my flights, even though I would actually pick the same flights. This would get me the $69.00 cost, but not the additional $25.00 off. There is no where under the change feature to add the promo code.
So...I thought I'd call and ask what my options were, and the very helpful SW lady let me know that I could cancel, have my funds put into an 'electronic fund', and then rebook at the new price..starting basically from scratch. I asked how long it would take for those funds to re-appear so I could use them again,and that I was a little nervous to do that in case I cancelled my original flights, and then by the time I tried to rebook, the lower price would be gone.
Well...she said, ..."follow me"

.
She stayed on the line while I started the booking process as a new customer, with the lower fare and the promo code. She stayed with me all the way through the passenger names, etc, and waited until it asked me how I wanted to pay. She then said, 'give me a second,,okay...go ahead and use your electronic funds'. It all worked!!! She waited until my new flights were all squared up, then cancelled my old one just seconds before I 'paid' for my new ones.
She was VERY,VERY helpful!!!
If this is what SW is all about...I will book with them next time I fly!!! (and that's not just because I have a $240. credit with them...lol
Just thought I'd share this information, in case there is someone else in a similar situation.