Maintenance fee double billed randomly

I have been with Nedbank for over 10 years now but I'm honestly not happy with one of the accounts that I have got with you as you are double billing me for maintenance fee which you do randomly. I usually get funds on the 27th but you guys bill me on the 11th or even on the 23rd, WHICH RESULTS IN NEGATIVE CAUSE I WON'T HAVE FUNDS THEN. AND WHY AM I BEING DOUBLE BILLED FOR MAINTENANCE FEE ON OTHER MONTHS? LIKE IN FEBRUARY I WAS DOUBLE BILLED AND OTHER MONTHS, CHECK MY STATEMENT AND SORT IT OUT!!