Unauthorised billing

I was called by telesales lady of Vodacom Direct Dealer that sold me a tablet with uncapped data. I received the new sim card but when the vetting documents came through, I saw that the data was limited to 1MB and the tablet was not worth the money they want to charge me monthly. Before I received the Tablet, I phoned the number the gave me and cancelled the deal on 15 October 2014. I still got the unused sim but did not receive the tablet. On 3 November I was invoiced for the full amount of R324 and every month since and it was deducted from my bank account. I called customer care several times at *** and even got a referance no S3/1T32P and a promise that it will be resolved by 15 January 2015 with a refund of the unuathorised deductions. On 30 jan 2015 the same amount was deducted again! This is ********!