Unauthorised debit order

There is an unauthorised debit order that keeps on deducting an amount of R4512, 64 every month and my bank FNB is unable to assist. I have been to the branch 5 times already, been on calls with the debit order people, spoke to the agents on the FNB app as well but no one is able to assist. The only info i have is reference name which is Absa Red pm. The number on the system *** is non existent, can someone please assist me with this.