I too am confused. "Thank you for providing us supporting documents. Due to nature of the claim, unfortunately the documentation received could not be used to contact the Merchant and therefore, we are unable to proceed with the investigation." The nature of your claim is easyJet didn't provide the service you paid for (they cancelled the flight). I assumed you provided documentation to show the itinerary you purchased, and the easyJet cancellation of that itinerary. I don't know why they can't relay that documentation to easyJet, or why that is in any way insufficient to establish that you are entitled to a chargeback.