Worst banking experience

I opened a current account last year with Nedbank, I moved from FNB because the charges were high only to find that Nedbank is even worse. Just todat i had R3190 in my account and I made a purchase of R60, an sms came in showing a remaining balance of R2760. You do the math. Does this make sense to any of you? It's not the 1st time I experience such. I really don't understand what the heck is going on. Sometimes id have more than what I thought and then at some point way less. I don't know if the bank is slow on processing transactiond. I'm not a financial genius. All I want is easy, convenient banking.