after submission of my article, I realize that it was a predatory journal. I ask to withdraw my manuscript but they require to pay half of charges. what can I do? If I do not pay, can I submit in a new journal? thank you
Could you provide some more details? In which country are you based? Where is the journal based? Is the journal WOS-listed?
Here are some basic orientations:
If you are certain that the given journal is a predatory journal, you can certainly retract the publication. Predatory journals are designed to maximise income and minimise expenditure. Accordingly, these journals are certainly not interested in a lawsuit (especially an international lawsuit). Emails are a matter of empty threats in that case.
If you are uncertain about the degree of predatory-ness, simply retract the publication based on the most relevant limition/flaw of your study. State explicitly that you feel that the quality of work does not fit their criteria of "high-quality, peer-reviewed science" (quote whatever the described on the webpage). Write the email in a manner, which puts them in "double bind" dilemma (https://en.wikipedia.org/wiki/Double_bind). Force them to either agree with the retraction at no cost, or to openly have to admit dishonesty regarding their "high-quality" peer-review process.
If it is just a low-quality but not predatory journal, be fair and go along with the submission this time and stay away from the journal in future.