Extention of my contract without my concern

On 21 Jan 2015 I log a complain at Hello Peter because Telkom Mobile extended my contract for another year without my concern while I was only doing a sim swop. I first sign a contract in Feb 2011, upgrade 6 March in 2013 and now in 2016 the contract is supposed to be over. I did send a cancellation form on the 31ste of Dec 2014 and explain to them it had came under my attention that one of their employees at the kollonade branch extended my contract while I was only doing a sim swop. I recieved a call from Telkom Mobile two weeks ago after the Hello Peter complain that they will investigate this, up untill today two weeks later still no feedback. They can see on my contract that the contract period is over, I want this contract cancel and the nr to be on pay as you go. I cant understand what is there to investigate this is not my problem if they have *********** personel. I want the contract cancelled and if this is not going to happen soon it leave me no choice to open up a ***** case against Telkom Mobile.