SWAVictor,
Today, I ran across the same problem as described by mritty above.
(OOPs! There is a problem with your form of payment. Please verify your payment information and try again. If you continue to receive this message, you may wish to try an alternate form of payment or you may contact a Southwest Airlines Customer Representative for assistance at 1-800-I-FLY-SWA (1-800-435-9792). (SW900001) )
I am assuming it is still an open trouble ticket?
The original problem is "supposed to be" fixed . . . note that in my original response I mentioned that this same error verbiage could be used for multiple different payment errors.
At this point, we are trying to knock them out one at a time.