DeltaWebGuy has informed me that Delta will issue a credit to the cc used to buy the walk-up fare for the difference between the walk-up fare and the advanced purchase fare that I originally attempted to buy. He says a few days are needed to process the refund and for it to appear on my cc statement. I am patiently waiting to see what happens. I have nothing but the highest praise for the DeltaWebGuy has stepped up to deal with this. Maybe we wil see a change of culture at Delta where customer service gets the attention that it deserves. I will post a note here when the refund processes. Thanks again to DeltaWebGuy!