getting billed after cancellation

Good day, on the 20th December 2015 I went to a Telkom store in Eastgate shopping centre in Johannesburg where i followed all the procedure to cancel my 24 month contract on my Samsung Galaxy which was about to expire. I was then told that on Monday 21st December 2015 I would get a call from the cancellation department to confirm the cancellation. I specifically told them the reason of cancellation was because I could no longer afford it. instead they send me an outrageous bill which is more expensive than the one I used to pay under contract. I then call Telkom and they tell me that there is a 21 working day procedure before cancellation. I was not informed of such a thing. and why do they bill you differently if there is a 21 day procedure. this is called misinformation and cheating on the customer just to get more money.i want telkom to reverse the bill as they failed to inform me of such an outrageous procedure. I also want to speak to someone in charge as no one understands the problem, and there is no complaint department. very unprofessional. My case number for cancellation is ***1.