Unauthorized online purchase from unknown source

Capitec is ****. Today just 1hour ago, they ****med me R900 something on my account as they debited money from my account without sending me message of authorisation for the online payment which l don't know of. And when l went to the branch they told me there is nothing much for them to do, they only thing they could help of is to block the account and open another one for me which they charge a fee. Why should the bank allow such amount of money out of the bank without authorisation as per the safety agreement guidelines regarding online purchases. I'm super frustrated and annoyed by these incident as it is not like something that l joined personally.