So, I bet no one at NI will do anything to protect their userbase against SCAM attempts.
I cannot tell if the scammer has hacked the site or if you can list all users and maybe also already have all passwords somehow.
The only thing I think you as a user can do is to either delete your account here or at the very least change in the settings so that either your email or username is not visible.
Home› Profile› Account & Privacy Settings
There are some really scetchy settings there that you should disable immediately. I recommend this:
Cheers, and stay safe!