Standard Bank ***** Case

Recently I was ****med out of R20000 on my Standard Bank credit card. The caller identified himself as a bank employee and unfortunately I believed him and gave him information. I am not disputing that I gave out the information that allowed the transaction to go through but I realised it immediately and called the bank to cancel it. They said they were unable to do so but did not explain why. My question is: for an amount that large, surely the bank should call the client to verify that it is a genuine payment and not *****? ABSA does that even for R200 when it is online banking. I complained but Standard Bank has steadfastly maintained that they are not liable. Similar cases in the UK were refunded by the Bank because Banking experts said that since the client believed that she was talking to the bank, the payment was not authorized therefore the bank should refund. The bank refunded her in full. In my case, the bank admitted that this was ***** since the person tried 3 times to get more money but fortunately I stopped those in time. But one payment went through and I lost R20000.00. I have complained but to no avail. Even the ombudsman has sided with the Bank in this case. How is it that the customer has to bear the brunt of *****? I was overseas studying at the time and caught off-guard when the call came. No mitigating circumstances helped me to convince Standard Bank to re-consider my case even citing the cases in the UK with NatWest Bank in exactly the same circumstances which was refunded.