unauthorised debit order processed by First national bank

I have been financially disorganised and frustrated by first national bank as they processed an unauthorised debit order thorough my account . i have a revolving credit loan with them .I have been paying it via transfer over a year now ,from my easy account . I did the transfer on 29.03.2019 and the D/O went off the following day 30.03.2019 and i contact ********** and i was told that it is not possible to reverse it because they dont have that function , even though i never gave a consent for the D/O.