Here's a tip I've learned when traveling with Delta - especially when I am on the road: Their customer service phone line is a crap shoot, but their customer service via social media (thus far) is golden. When stuff like this happens, immediately hit them up on Twitter (@deltaassist). Do this in addition to what you did on the ground. I've found, for whatever reason, this web based customer service team can "see" a lot more in Delta's computer systems than a GA or even phone rep can. I don't even book complicated trips any longer via a phone agent, I have Delta Assist find and reserve a flight fore me. I know Delta has had a bad record in the past with customer service, but try some of these new tools. I've found them extremely helpful.