They're most likely Cayugas. That is what I would automatically think if I didn't know. They are too big to be BEI and it is doubtful they are Black Swedish based on the coloration (of not only the down, but also the feet/bills). Are you questioning whether they are Cauygas because of the yellow in the down? If so, that is pretty normal. A lot of Cauyga ducklings have that. In my experience, Black Swedish generally (note that I said "generally", not "always") have much more yellow down which also frequently occurs on the wings (what will in most become the white primaries, although not all have this) and they also more often than Cauygas do not have solid black bills and feet as ducklings. Of course, some hatchery quality Cayugas may have those things as well.
Anyway, I remember seeing your thread yesterday. Didn't you have 6 shipped eggs, 4 of which developed to full term with these 2 hatching? If so, you did pretty well for shipped duck eggs. I would not be at all upset with the seller. I am not clear why exactly you would be upset with the seller, unless it is the yellow down? Maybe you can clarify.