Double deduction

In December 2015, multi choice made a double deduction from my account. When I followed up I was told they can only see one premium of R828.50 on my account and I must send my bank statement and the turn around time to solve the problem is 3 days. I followed up on the 4th day and the matter was still not solved and I was informed to call after 7 days. I called on the 8th day and I was told the matter was being investigated. When they finally called they said that I was paying for two accounts, but they could not explain to me how this happened as I have never authorised such a transaction. I was informed that in January 2016 there will be no debit as I have credit