Nedbank doesn't care about their pensioners

My mom recieved a call from Nedbank asking telling her that some company is trying to withdraw money from her account. She answered the questions asked believing that its truly Nedbank. After a few moments after the call money was withdrawn from her account R14000 . As a result my mom suffered a mild stroke, My mom is 68years. Today they called her saying the case has been declined. My question is wasn't the bank supposed to protect her as there client? Where did they get her numbers? How did they get hold of her account? So this means poppy act. How could they go so deep as withdrawing money from her investment? Now Nedbank is saying they will reimburse her with R3000 since the case was declined.