FNB is inconsiderate

I opened a new bank account with FNB. I work on a monthly budget and FNB has gone and debited the last money I had to take me through this week until the 25th of the next month. When I opened the new account they failed to ask me which date I would like my bank charges to go off. I find this really inconsiderate of FNB and cannot understand why they would take bank charges on the 16th of the month and not the date that I get my salary which is the 25th. I am disgusted, that was my money for bread, my daughters Friday tuck shop money. I need that money.