Treatment unfairly

In 2023 July I went to cell c store, the Agent told me they running promotion you get router with 50GB day 50 GB night for R 234, if I'm not mistaken, I agreed and I took my router on that day. First deduction from my account was thae right amount, but end of November they took R 255, when I asked they said" every December the money increase, I asked them but I signed the contract on 232, for 24 months to pay, how can they change the contract, their money goes up from the contract that I signed for 234 to 290 now, but their datas remain the same. So what I need them to do now I want them to tell me how much outstanding so that I can pay and separate with them. I will never ever apply any contract with cell c. Now I do t have network because I reversed R 664 they took from my account end of February 2025 because I don't want to continue with cell c anymore. They took advantage in to my bank account. I need help.