Bad customer service

For the past two weeks I've been trying to cancel some of my Vodacom contracts and have been getting the same response, i.e. that my profile is on the old system (I have been a client for more than 20 years) and that no one in their cancellations department has access to it. I'm then told that someone will call me back as soon as they have access, which just doesn't happen. I phoned again today, 21 July 2020, and after receiving the same response, I refused to hang up as I wanted to speak to a supervisor to understand how this can be resolved. I was told by the agent that she has sent the supervisor a message and that he/she would connect soon. Needless to say, nobody connected to my call, I was on hold for quite a long time and eventually had to drop off. The call duration was close to 30 mins.