Vodacom strikes again!!!!

I am utterly disgusted at the call I just received from Vodacom. I took out a contract with Vodacom in October 2021, (Red 500mb, 50 min package). Now I get an agent calling me telling me that they have noticed that we have topped up on the number (which the contract allows) and now they are putting me on a Red 1Gig, 100 mins plan). I have not topped up on this contract and when I asked the agent to confirm what the amounts are of the top-up, he says he cannot see. This pushes my contract from R310 to R425 per month. When I said I am not interested, he tells me that I have no choice, that is what Vodacom is going to do. In which universe is this allowed? The contract allows me to top up and even if I do, how can Vodacom force me to take something I do not want. I signed up for my contract over a period of 36 months, so If I don't have the right to not pay my contract or renege on my contract, then how can Vodacom just make changes to my contract midway through the contract period. Somebody urgently needs to tell me what is going on at Vodacom? Is this how you treat your customers?