looks like this is not the first time Nasterxchange had an issue with other people. sadly just like what the others have said scams are not moderated so there is no chance of him being banned because of it. that being said, if you have convincing evidence you can create a trust flag against him.

I'll refer you to this thread to know what it is and how to create one [GUIDE] Overview of the trust flags and to this thread Request Support (or Opposition) for Flags here! to ask members for support.