This is fraud. If it's trivially provable the product is not counterfeit, then what they did is criminal. Not civil.

If so, it should be documented. All the evidence with relevant vendor contact information, accounts, dates, events. Each state has their own consumer protection laws, so as this involves interstate commerce who to report it to will vary, but you can start by calling local police. They can tell you about jurisdiction, and escalate to stat consumer protection division. And states work together with the FTC on such cases as well.