Unknown contract registered on my name

I recently went to upgrade my phone when the Cell C assistant told me that I have two contracts registered on my name. When I told him that I only have one contract, he informed me that the other contract was taken out on my name about two years ago. I have never given permission to register another contract on my name and I have thus been paying for this contract for two years. The monthly payment is about R440 for a phone I never knew about. I laid a complaint with Cell C on 30 November 2015. They informed me the following day that my complaint has been transferred to their ***** department who will contact me within two days. Despite various e-mails and calls from me, I have not received any response. The only response I got was a sms asking me if Cell C can deduct my debit order two weeks earlier in December. So basically someone used my name to register a contract. Cell C therefore has no security on their clients information.