Contract

I have a contract with MTN and it is terminating on the 16th of March. Last month on the 17th of February I called mtn to inform them that I will be canceling my contract. I was told the contract will terminate on the 16th of March. To my surprise, I get a message yesterday that I will be on a month to month contract. I then immediately call mtn to inquire about the sms I got. The lady said my contract is terminating on the 16th and I must call again after the 16th to confirm the cancelation. Today again I receive another sms stating the month to month contract which I never authorized. I need answers from them because I am not going to let them deduct my money come the end of the month.