debited twice

I went to shoprite midrand to make a cash withdrawal first cashier they don't have money secondly the other cashier her speedpoint is not working finaly the 3rd cashier debited my account twice with R800 instead of R400. the service was bad and the cashiers must be trained on how to use the speed point she said that the transaction declined but she never gave me the reason why, I had to put in my pin twice.