Fnb charging additional fees for account being in a minus

My name is Edith Smith I have an fnb aspire check account. I am currently unemployed and I usually have a debit order that runs every month for pet insurance. I canceled my contract with them as I did not have any funds available in my bank account. I was made aware that the debit order would still go off because I had to let them know a month ahead but only let them knew a week before but the consultant told me I could just reverse the debit order. But instead of Fnb just putting my account into a minus of the funds of the debit order they charged me an extra R200 because the card does not have funds available. I already don’t have funds available and they charge me extra because the account is in a minus.