Bank Statement and Cellphone notification

I went to withdraw money in my account on Monday 30/11/2015 and after I entered my pin the card got spat out and the ATM message said system error try again later so I thought the money expecting not in my account and I tried again and this time I check the balance and withdrew as I was expecting 2 payments. I did not get a sms notification for the withdrawal and went inside the Bank to verify whether the second amount of R2500 was also deposited and did not report and asked for a Bank Statement and was told that the system was offline hence why I am not getting sms notification. On 02/12/2015 I requested a Bank Statement as the second amount still did not register on my sms notification and was not on my Bank statement. On 03/12/2015 I went to the branch as I was unsure of the Bank statement and the transactions that I swiped on Saturday did not go off until 03/12 and the agent at the branch called Head Office and Palesa said I owe the Bank R435.86. I need to know why I owe the Bank for their error and I refuse to pay I do not know of, if the money was not due to me why was it in my account in the first place?