Unauth upgrade

I Willem A Punt never consent to the upgrade of the contract during December. The phone contract was upgraded by the device according to Vodacom, I haven't agreed or consented to upgrade the contract and no proof can be provided by Vodacom. The contract I signed was for R268.99 per month, since December R810.00 pm was deducted from my account. The call Centre advised me that they will only downgrade once I have paid the R1,070.00. I refuse and insist that the charges are reversed and that the initial contract is re-instated. I will pay the amount of R804 once this charges is reversed and confirmation received that my contract is downgraded (This will include the arrears for Dec, Jan and installment for Feb).