Alright, rather than chastising the writer for their experiences and understanding of the industry, how about this instead?
First, when choosing places to publish through or accepting deals, take a look at the “Writer Beware” page by Victoria Strauss. There is a rather large and curated list of companies that writers should steer clear from.
Second, a quick search on the Better Business Bureau can also inform a decision when looking at a company.
Thirdly, when considering becoming published by someone, I encourage you to look up specific copyright terms in a contract. Ie: there’s a difference between first buyers rights versus exclusivity rights. In places like KDP or Smashwords, there will be a document to read that outlines what kinds of rights you retain as an author and what rights the publisher has to your work. It is important to read and understand these agreements.
Hopefully, this helps for future agreements you pursue.
