No assistance for a pensioner

I am writing this on behalf of my mother who is a pensioner. A debit order went though her account now for >R19k? She contacted MTN and was advised that it is *****. Now her number is blocked and every time she contacts the MTN service desk, she is being send to another department and nobody seems to be willing to assist. She cannot go into a MTN store; she is over the age of 70 and due to COVID she feels unsafe to leave home. My brother also tried to sort the matter out however was told that she must give permission for him to contact MTN? How must she give permission? This is an old lady and how could she have accumulated an account for >R19k; she does not stream movies and does not use her phone apart from calling and sending messages. Is this how one treat an elderly; are you also now going to tell me to get her permission as well? Permission to try and sort her billing out; she has now been stranded and what happens if she has an emergency and cannot make a call due to her number being blocked. Shocking service to say the least. How will MTN resolve this?