Billing for contract with Vodacom

In November I renewed my contract for data and December I renewed contract for phone, for data the contract is R349 and for my phone is R179 which I should be paying R528 per month, today my account has been debited with R1379. 18 which I don't know of and when I call Vodacom I was told that I upgraded my data contract on the 24 January which I don't know anything about it and I didn't authorize any Vodacom to upgrade my data. I would like Vodacom to reverse whatever they have done in my account and reverse back my money or cancel everything that I have with Vodacom within 12 hours.