Hackers calling pretending to work in the bank!!!

Yesterday around 6pm, my helper received a call from the following number +***5, the guy was stating that he is a consultant from Tyme Bank named Thembelani Ndlovu or something like that claiming that someone from PMB was trying to hack her account, and that he needed her ID number to avoid this person from hacking the account. She did inform him that she has the app and that if she needed to block her account she would do it via app. She also alerted him that banks are closed at the time he called so why is he calling now after 5pm, he then dropped the call and throughout the whole call, he only spoke Zulu to her. He asked her questions like whether she is receiving the R350 grant or normal sassa grant, then when she said its her salary that she uses the account for, he then asked her how much is in the account and she answered 0.00, that is when he asked her for her ID number so he can block the hack on his end, she said no ways she cannot do that, if he is working in the bank why can he not block the hack without her confirming the ID number if really it was the case!!! How can her account be secured from such things happening again coz now she is afraid to put money in her account afraid that they might of tried something even though she did not supply any of her personal details.