Ex-NBA lottery pick Noah Vonleh is on a "malicious harassment, defamation and extortion campaign" against his former sports agency ... so says the organization's legal team, which tells TMZ Sports the athlete is entirely in the wrong.
The 29-year-old Indiana Hoosiers product has been on an incessant rant against the Chinese Basketball Association's Shanghai Sharks and the Pensack Sports agency on social media in recent months ... claiming the team and his reps stiffed him out of money he was owed and treated him like crap.