Did I buy a fake phone off of ebay? Help?!

I bought a factory unlocked Samsung Galaxy s6 on ebay yesterday, and I didn't notice till after I bought it that it said "3g data capability." So I questioned the seller, and he said yeah, because of the bands or something and that it depends on which carrier I get. He mentioned the carriers and I said that they wouldn't work for me, and I said verizon would do. So he said he could get me a Verizon one which would do 4g lte and has a 4G lte simcard.

I looked on his feeback, and most of the other people who bought the same phone gave him positive feedback and said it worked good. But I'm really scared and I feel stupid and sad and anxious because school is starting and I jumped into this way too fast. I also spent a lot of money on this. Is it fake? I'm scared.
Added (1). Also, the seller is apparently from America.

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