Why am I paying for something I don't even have?

In january 2016 a modem was sent to me without me ever agreeing to get it. I never spoke a sales person, never agreed to have a debit order on my account and never wanted the modem. I went in to the cell c branch in carnival mall and they were unable to help me. EVERY month I have to go into FNB, reverse the money back into my account and this is a schlep.The catch here is that I already returned the modem to cell c, unopened and never used. What kind of company are you running? Why are you taking my hard earned money for something I don't have. I have spoken to your ***** department, I have sent in all supporting documents, affidavids, the proof that I returned it and so forth. I am thinking about taking legal action. How many more timesdo I have to explain my case before this thing I never signed for will be removed from my name? I am sick of this!