Contact Amazon and see what they can do. Try and create a portfolio indicating that it is your competitors that are the one's doing it (which will be tricky).
happening to me now. can't believe it seems to be nothing but a lost cause. yet i get emaisl every day from AMZ boasting about how they love their sellers.
neg feedback, a-to-z claims and reporting my items as dangerous. had to put account on vacay before it's too late. and of course AMZ customer service has ignored me on every attempt.