#item paid no funds charges

I've been using FNB from 2009 and the past few weeks I've never logger into the app because I wasn't using the card to transect and today when I logged in, I'm on -R1200 due to #item paid no funds worth over R700 How is that if there's no money into my account the payment just decline with "insufficient funds" than to accumulate such amount over things I'm not even aware of? This is madness