FNB RESOURTS TO HARRASSMENT

So after reversing all my debit orders this month and for charging me R840 for them, FNB, is threatening me with legal action after this months debit order for a revolving loan was reversed and I was charged R120 for the reversal. I just find it strange that they are threatening me after my initial review of their services. Even though I did resolve the issue with them prior regarding the revolving loan. It feels like I am being harassed.