allowing debit orders to run with no balance

My company changed its payday to the end of the month, two debit orders run on the 24th, however my account balance was near zero on the 24th, yet FNB decides to still let the debit orders run, making my account go into the Minus, then demands payment a day later, What kind of nonsense is that, and that's clear breach of my account, next time this happens ill report it to the ombudsman and get you to write off that money. Honestly FNB, What nonsense!