Seller contacted me to not sell their product.

I bought some items from Alibaba and started selling them on Amazon and one of my products sold out in less than a day 100 count. I got a message saying that I should need to stop selling their product and they said my product is fake. It is not I tested it myself. They do not have a label and their are other sellers selling it. Is this fake to get me to leave the buy box or should I be worried? They said they made my listing unsaleable somehow idk I think I ran out of inventory first but is this legit? Low key freaking me out cause I wanna sell them again.