I WANT TO CANCEL MY CONTRACT WITH MTN

I called in MTN on the 2nd of October 2015 requesting to cancel one of my contract cell phones as my contract had expired. The consultant told me that it will take 5 working days for the cancellation to be made. On the 9th of October I called in to find out how far are they with the cancellation and they told me nothing has been done in this regarding. Since the 9th of October I have been calling in everyday to try and cancel my number but they are busy taking me up and down as if they do not know what they are doing. I am very frustrated with this.