I think I should leave fnb

I am thinking about changing banks a debt order or R674 did go of my account on the 2nd now thos is not the amount I agreed on with the company when I accepted the debi check so I called the company and they said I must ask my back to reverse and dispute it and that's what I did and now fnb is telling me they can't reverse it what type of bank is this my money is not safe with this bank akd fnb is so unhelpful