Ignorance from the Vodacom cancellation department

I don't understand what is suppose to be so difficult about cancelling a contract after the 24 months. As my contract was nearing its end, I contacted Vodacom a month in advance to cancel my contract. After speaking to the consultant for a while and him trying to sell me other products and me telling him that I am not interested, he eventually told me that he has processed my cancellation. I was shocked to see that I was still then getting charged after the 24 month contract ended. I contacted Vodacom cancellations again, only to be told that the cancellation wasn't processed. I was frustrated and really upset because it is my right to cancel after my contractual period and they just don't cancel after requesting it. The second consultant also tried to sell me other products. I kept on telling him all I want to do is cancel. This call took longer than the 1st one and he assured me once again that it was cancelled and that they would investigate the matter. Once again, I got billed on my next statement. By this point I was livid. I called in again for them to eventually cancel it. The consultant said to me that they would investigate the matter. I have still not received any feedback from the investigation regarding the cancellation. This is not the 1st time that this has happened. Really poor service. Not impressed at all