In this case the person who quit was me.
Agency didn't pay the past 4 months, we asked at least the reimbursment of expences.
They told in a 2 hour arrogant speech that we must thanks them becouse they make us work even if they aren't paying. They said that "in this period these are the rules and we must accept this condition." So, I stand up, I went to shake the hand of the boss and others, I went to the door saying "good luck".
All the coworkers stand up and applauded.
Two months later the agency was closed declaring failure.