Parents of DL, DL tech, and Comair employees can fly for FREE domestic. It is a paper ticket and it is issued by the same means as a ZED ticket, but there is a slightly different pricing entry. What city were you in? It's funny, as a sub-par, non Delta Air Lines agent, I've taught so many real life Delta Air Lines agents how to sell me a ZED ticket or a NW flight coupon. It's funny too, because you don't want to be pushy, but sometimes you get a newer agent or maybe an experienced one that still doesn't know what they're doing, and you need to find someone else to help you. You also might be in a city that DL has contracted out to Worldwide Flight Services or some other contractor. Also, it will become increasingly more difficult to get quality service in smaller stations in the near future as some of the best employees of Comair take their talents to other airlines rather than "RHS."

So, you were misinformed at the airport.