The easiest way to deal with a dishonest or illegitimate publisher is to avoid them in the first place.
Know your rights
Until you sign something, you own your copyright. You may share ownership of a work with coauthors, but only you can sign your share of that ownership away. A publisher's leverage rests entirely on securing your copyright from you; until you transfer your copyright, you have the leverage. Resources like the Authors Alliance or SPARC can help you to learn about what that leverage means for you.
Don't take an email from an unfamiliar publisher or journal at face value. Use a checklist, like Grand Valley's or DOAJ's, to investigate and evaluate before making any commitment.
Raise your awareness
Do your homework when considering an invitation to publish or serve as a reviewer. Who is it that's asking for your scholarship or your time, and what are their practices? Don't wait to find out until it's too late.
Pay attention to who publishes the journals you're considering; reach out to colleagues listed as authors, editors, or reviewers before you commit to anything to verify their affiliation with the journal or publisher. An illegitimate publisher will often list people as editors or reviewers without their consent.
An organization to advance the interests of authors who want to serve the public good by sharing their creations broadly. Includes resources to help authors understand and enjoy their rights and promote policies that make knowledge and culture available and discoverable.