I have had a similar situation more than one time. Once Delta allowed me to fly home early from SE asia to get home to a sick family member, and the other time delta allowed me to cancle my flight and I received an e-voucher for the total cost of the ticket minus the change fee of $250 since it was an international booking. BUT, DL also waved the changed fee, it just meant when I wanted to use the evoucher I had to call Delta, book it over the phone, and they then used the e-voucher +$250, in turn giving me my full amount back