Gathering proof and reporting the infringement to Amazon\’s Seller Support are two ways to get rid of an unauthorised seller from your Amazon product listings.....
https://openarticlesubmission.com/protect-your-brand-how-to-remove-unauthorized-amazon-sellers/

Removing unauthorized sellers is a crucial step towards regaining control of the Buy Box on online marketplaces like Amazon, Walmart, eBay, etc. By doing so,....
https://i2oretail.com/brand-protector/