Was this purchased through Delta? If so, send in a shortly worded complaint to Delta and specifically mention EU261/2004. I was given $400 Euro compensation for a cancelled CDG-AMS flight (on AF that was part of a Delta itinerary). It did not take long at all to get this (a few weeks). I was sent a check in the mail directly from Delta (although I never corresponded with AF directly; I believe the money came from AF).