Most likely they won't respond and will just be taken down. They might file a false counternotice but if so you'll get their contact information and shouldn't be worse off than if you'd done nothing.
If you're on the fence because you are concerned that the scammers might retaliate, keep in mind that if you knowingly allow scammers to defraud people under your name when you could do something to stop isn't the most moral choice-- even if its the easiest one.
Then again, I'm currently targeted by a multibillion dollar lawsuit because I called out a scammer in my former industry, so maybe don't take my moralizing at you too seriously. :)
A lot of these platforms will limit or ban accounts that accrue DMCA takedowns. Sumbit a new takedown for each instance of copyright infringement you find.