Dropshipping my product on ebay

I found someone dropshiping my product on eBay, am not sure if I should be concerned as they are kind of helping my organic rank on Amazon, am not yet trademark so am not sure if I could even stop them. has this happened to any of you and if so how did you tackle this situation?

Answer: Start selling it on eBay yourself and knock a couple quid off it, there must be a market for it on eBay if someone is going through the effort to steal it off you, and add generous promoted listings.