Debited on wrong dates, paying charged unnecessarily

My FNB debit orders have been going off on the last day of every month, but for the past few months I am being edited on the 21st or 23rd, which means I am being charged R115 for insufficient funds. at times, they debit twice on the21st. So where does FNB expect me to have that money when it's not payday yet???

When I call, I am told that they will escalate it or I hold forever only to be cut off. My time, by money and energy being wasted with no assistance.