Vodacom overcharging

I entered into contract with vodacom May 2022 and I took a A13 samsung smart phone for R258. The contract included 650 data and 50 all network minutes. However now vodacom for a year now they are charging me R274 including headset which were not part of the initial contract. I see they sent me the bill for this month and it's R292 which I don't understand why. I went to their shops where I took the initial contract and asked why I am paying a different amount to the initial agreed amount and they did not have an answer. I asked them to return my contract to the initial R258 we agreed and to this day, that has not happened. When I reversed their overcharged amount they list me on credit bureau as if I don't pay my bills. I want vodacom to take my contract back to the initial contract of R258.