FNB slogan "how can we help you?" No ," it should be how can we help ourselves to your money "

I have been an FBN bank client since 2021 and I never asked for thr bank to allow debit orders if there's insufficient fund in the account, last month I saw a fee charged for " letter of demand " when I went to the branch to enquire. I was told its from FNB for the money outstanding....I was puzzled cause I never took out any loan or credit card with them. I later found out its because they honoured 2 debit orders without my acknowledgement and charged me a fee for a negative balance and I wa expected to psy it within 48 hours hence I received a letter of demand. 12 days later money was in my account and FNB took it to balance all the transactions. My question to them was 1st I never requested or authorised that functionality in my account , 2nd I was not given even 30 days for the account to be corrected which as my bank should know to give 30 day notice to have funds available in my account. Which consumer law that says allow transactions in my account even if I don't have money in the account??? Meaning as a bank your causing me to be overly indebted?? My matter cane back saying I was supposed to settle the excess amount within 48 hours regardless of the cause.I ended up paying for the debited amounts, the excess fee, the letter of demand fee."Talk about consumer protection from our bank"?