Missleading SMS's

My wife and I used the card to pay for our month end item like every family, groceries, bills ect. and every time we use the card we get a message to say how much is left in the account. Then Wednesday morning comes round and after budgeting for everything according to what the messages told us after every use we awoke to find the we are just over R1000.00 in debt and still had to pay late charges on items not taken off that same day as the sms's have told us had happened. How is this possible? this is not the first problem we have had with Nedbank and our patients is wearing very thin and considering closing the account and moving to a new bank.