billing for an account that was cancelled

I settled my Vodacom account on the 11th august 2015. I spoke to a number of people on that day to send me a settlement letter and to cancel the contract as the numbers has been deleted. on the 24th of august 2015 I had to call again as I have still not received the letter, I was transferred from one department to the other and everyone giving me a different story. I received today a notification stating that I owe R785, after I have specifically asked that it be cancelled. I have called again and have been transferred to 4 different departments, when I get to the legal department I get to someone that sounds like she hasn't got a clue of what she is doing, I have been a Vodacom customer for many years I have a contract for over 8 years and I'm appalled by this level of service. I need this to be sorted out ASAP or I will be forced to take the matter further.