CANCELLED CONTRACT NOT CANCELLED FOR OVER 2 YEARS

I have cancelled one of my data lines which was supposed to be updated in 2015. I saw the number on my accounts after that and went to the Vodacom stores. They assured me that it is just “laying” there and that I am not paying for it. I went into my online account again and really start looking around and saw that some of my lines are put together on one invoice and that I am still paying for the line that I cancelled. It is now 2018 so I have been paying for 3years for absolutely nothing.????? I want to know why was it not cancelled and am I getting my money back. I did not use data on it as I thought it was cancelled years ago. Please I want my money back. I spoke to an agent again today, he said he will cancel it again and offered me a smart tab which I did not really want to take as I do not want to deal with Vodacom anymore. This agent also told me that I have plenty of data on that line. So am I also loosing that now??? Please help me to sort this out.