#Item paid no funds every time

I'm very disappointed and cross with FNB,I mean I have been with FNB all my banking life. Now there is this thing called #item paid no funds It's been few months I have seen this trend on my account I have lost hundreds of Rands because of it .. I mean you can't buy something without money in your bank.. every time when my bank is R100 or less this ridiculous chargers pops up.. I get to pay over R1000 every on this and bank fees on my cheque account.. I'm leaving them what ever I owe will pay it from another bank