*****ing my money

I had one contract with Vodacom which was R109 per month and then suddenly they started deducting R360. I phoned them and they said I opened a new data contract on my name. I explained to them that I have never opened any additional contract and I haven't even used the previous one in the last year. The more I tell them I did not open a new contract the more they said I have. Vodacom is *****ing my money as their answer is just they will investigate, but I dont get any further answer out of them. They cannot even give me proof that the contract was opened and cannot tell me what the data is used for.