Contract Cancellation

On the 25th of September 2015 i signed a contract with cell c. In August 2017 i contacted them to cancel my contract because it stated that i must give them a months notice of which i did. On the 1st of October i switched on the device to check if the contract was cancelled and unfortunately it was because i received the monthly benefits. I then contacted the retention department and i was told it does not appear on the system i must go to the nearest branch and it would be cancelled only to find out i was just wasting my time and fuel and now i have to pay another month for a useless service.