Thanks for the feedbacks. The problem is that if I want to call Delta as I'm flying blue and based in the UK, I'm going to end up talking to a AF/KLM agent at an overly priced minute.
(I did call 3 months ago and I wasn't happy about the extra 11£ on my phone bill).
So I have no way to talk directly to delta, unless I call their US number, other than twitter.

I believe that the agent on twitter referred to his supervisor and I really really pushed to express how unhappy I was but nothing else could be obtained ....