Bad service

Today my mom visited your branch at Standard Bank Elim Mall, she accoumpanied her father to do a new pin since he lost his pin code for his card. My grandfather is over 70 and he doesn’t know anything about banking m. All my mom wanted to do was to have signing authority over his account so that he doesn’t go up and down if something happen to his account. He wanted my mom to take over and have signing powers on his account because he is very old and with this pandemic-covid 19 he is in high risk so he can’t be going up and down to the malls.But one of your staff refused to that for him, they deny him and say it is not possible to give her signing powers. I want to know from standard Bank how true is this? Can you please assist in handling this query.