Refuse to cancel a contract that's fully paid off

Last year agent name Modi from Telkom was approach with regards to cancel my mobile contract in August 2015 as the contract had come to an end but the stop order was still going through in my account. As time went by statements of payments still going through my account were sent to my house and money was still being debited in my account . Earlier this year (2016) I approached Telkom in festival mall to let them know that I app**** for cancellation in 2015 and yet I was still being charged for somehting I had already paid off they didn't get back to me as promised. In April 2016 I went to the store at festival mak three times with regards to my contract being cancelled and I was told my case hasn't even been looked at by them and they put me on their Nido system not even considering that I had app**** for a cancellation last year. The last time i approach the Telkom store in festival mall was 12 April 2016.