Absa insists I must visit their useless branch

My mother has an account at Absa. She is 90 and has dementia and I have power of attorney for her. Her old cellphone number of 5 years ago is still listed on her profile. Nobody in the universe can remember that number. Absa refuses to change the contact number to my cell number, requiring me to schlepp in to their (very inefficient) branch. I cannot do online transactions for her because it sends the OTP to a non-existent number. Nice one Absa