End of contract

I have a complaint which no one Is willing to help. I upgraded my Vodacom contract on the 09-03-2022 for 24months, I am due for an upgrade now to my surprise they telling me that my contract in on a 36months which I did not consent or agree to. I lodged a query in January, and they listened to the recording and came back with that their agent Gover003 made a mistake the recording states that the contract was for 24 months at R839 but they have been debiting R1040. Now they do not want to cancel or reveres the mess they made they offering me 10g of data for the amount I pay or return the phone so they can cancel the contract. I paid 26k for My phone which they WANTING me to delete my personal info because of the incompetence of their Agent. I WILL NOT PAY ANYTHING FUTHER THAN 24 MONTHS AND DO NOT WANT ANY DEAL FROM YOU (REWADSCO). Can you please do as the contract states that’s it. If I return the phone, will they give my money back or what? Please make it make sense. the recording says 24months and i am forced to pay for 36 or return the phone or else get blacklisted.