Consultant upgraded my contract without my Knowledge

I am really disappointed with Vodacom, my brother had a cell phone contract with Vodacom that was ending on March 2023, On February 2nd he called and asked for a cancellation which was not done, he called them the whole of February asking for cancellation and still it was not done, a consultant from Vodacom called him to offer an upgrade for airtime and data for R280 Monthly, my brother made it clear that he was currently unemployed and cannot afford the upgrade, however, the consultant went and activated the upgrade without my brother agreeing to the contract, they went and loaded the airtime and data, we called them and asked them to reverse it because my brother will not be able to pay it, they did not do it, we logged complains and they say my brother must pay it, at the moment an unemployed guy is setting with a bill of R580 because of your staff incompetence, please advised which act says if a contract is activated without your knowledge you will be liable for any fees or charges accumulated on that contract, I will be waiting to hear from you. At the moment my brother cannot use that sim card, and that is inconveniencing him because he is in the market for a job. What the agent did was ***** to push sales, why is Vodacome promoting ******** activities and letting consumers pay for it...Please this must be resolved before we take further steps.