Accidentally submitted to predatory journal (very naive and stupid first time researcher here) accepted with no evidence of peer review. Could not pay submission fee so they reduced cost substantially so I submitted an updated manuscript. Then realised it was predatory and they also have already uploaded my article online! Have not paid fee and confronted journal on predatory status. Can I get away with not paying the fee? No copyright transfer signed.
I am not a lawyer but I would think this depends on the contractual laws that govern you where you live and where the journal is based. You may be able to ask them to take down the article but they may try to do so through a retraction rather than simply "deleting" it.
On the other hand, if you have not transferred copyright then they shouldn't technically be able to publish the article, and you should still have had the right to withdraw the submission.
So this is a bit of a thorny situation and I would try to seek out help from your university (do they have a Legal department in the administration?) to guide you through this process.
Don't pay them! Pretty much no matter where you are, they'd have to win a lawsuit in a court that has jurisdiction over you to force you to pay. (If you and the publisher are in the same country, you may need legal advice; otherwise, you're pretty safe. I am not a lawyer and this is not legal advice.)
Sadly, the paper's probably a write-off, though, since they've "published" it on the web.
If you made a contract with the predatory journal to pay the fee, you must pay. You probably did not, but we cannot determine this for you. You cannot make a contract by accident if assent is required in your location.
If you did not make a contract to pay, then in my view you have an ethical obligation to refuse to pay. If you pay, you are supporting this journal's efforts to scam other authors.