Complete lack of service / incompetance

I have been trying to assist my 80 year old mother to cancel her account with Vodacom for months. She has not used the account in over 5 years and cannot get through to anyone at Vodacom who is authorised to cancel it for her. Every time we call, there is a problem with the level of authorisation the person has, we cannot access a manager who does have authorisation, no one calls back. In desperation she cancelled the debit order on her bank account, only to have Vodacom debit two months payments from her account the next month. Can someone please contact me asap to resolve this matter.