Collecting from wrong account because of their system error, they refuse to accept their fault and treaten to blacklist me.

They send me a message that they will blacklist me, they do not want to accept that they were the one faulty by attempted to collect on my pay date from the wrong account of their own but saying they" attempted to collect on your pay date from your external bank account on 27 November 2019 and there were no funds of which is totally lies I did send them my statement as per their request 3 months bank statement. Instead of accepting their poor system of work and assumptions that I had insufficient funds they threaten to blacklist me.