AFAIK the rule still stands that if you purchase a nonrefundable fare and then upfare (after the 24 hour free cancel period, which means midnight of the next day in DL land), the money that was originally nonrefundable remains nonrefundable. If you cancel the ticket, at least that portion of the total ticket cost will be returned to you as an eCredit, not a refund to your original means of payment (credit card).