Misselling by MTN company.

I have been on MTN contract for more than two years now and everything was going on smoothly until sometime in September this year when I received a call from one of MNT's marketing agencies ,'Rewards co'.I was informed that my contract is coming to an end this coming December so I was up for an upgrade.But what the lady didn't tell me is that she was putting on another contract.I told the person repeatedly that I can't afford and i don't need two contracts and the lady assured me that the one she was selling to me would substitute the current one. It was only when I received the router that I discovered that the person **** to me.So I went to complain to complain to one of their outlets in Montana Pretoria and I was advised to go return those items at Menlyn branch,which I did.But instead of canceling that contract I was informed that I still have to the people who sold me that contract and I did that the following morning. I was told that everything was fine and their system reflects that I have returned the Items and that they are going to cancel the second contract. But to my surprise on the 25th of October when the debit went off they had billed me more than twice my premium.I need MTN cancel the 064 number they have given me under false pretense.The only contract I know is that of ***.