Those heels look to have been cut down. I'll try to edit the photo later to show what I mean.
I'm surprised (a) the seller wouldn't take them back and ( you lost the case. I suppose the seller saying they were "more like a 9" (EU43) may well have covered some ground, but a shoe marked EU44 that fits like an EU42 surely qualifies for "significantly not as described"? Maybe not.
When I list something I always 'advise' on size, and often compare the like-for-like sizing against other brands. ie. "The shoes claims UK8 but fits like a New Look 7, and a Primarnie 7." Only had a single complaint. Soon after the shoes arrived with the buyer, she claimed they were a bit on the small side. They fit me with room to spare so I didn't accept her return request. (Felt she was B/S'ing.) Only later when she got feedback for a cheaper pair she had bought two or three days after bidding on mine, did I find she'd bought a second pair the same size, indicating she was a liar and just wanted to return the more expensive of the two pairs. The second pair were an identical shoe in the same size, only a different colour.
I suppose you're only allowed one 'case' too?