Originally Posted by
3Cforme
The details of the Delta ticket receipt are important.
The OP isn't going to like this answer, but under industry convention his beef isn't with Delta - it's with the operating carrier. Delta - irrespective of the booking on delta.com or 006 ticket stock - is simply the agent for the operating carrier. If the Delta reservation receipt and ticket receipt show a fare class and cabin that map to Business, KL needed to provide it. I suspect the best avenue for cash compensation is the EU cabin-downgrade compensation rule.
http://images.delta.com/delta/pdfs/eu_notice.pdf
I don't think the EU rules are a big help here. The question was a fare bought in Y that was shown to the OP as being in C.
The transaction occurred in IST (is that in Europe or Asia?), via a US website on a China carrier.
The best is trying to get DL to understand what happened.
I doubt the OP will be made whole, but he should get a lot more than a few thousand SMs thrown his way.