Lying Sales people and call centre agents

I've been struggling for almost a month now to cancel a fibre contract I have NOT signed up for. The documents we presented to me as a 'pre-approval'. "Ma'm I ensure you this is not a contract; this is just a pre-approval" was the words from the sales person. Now that I actually do want to signed up with MY choice of service provider for fibre, I have an 'active' fibre line (which I have never used, could never have used because there was another fault on the fibre line that first had to be fixed, I haven't even received a router or have it installed) and Vodacom just don't get so far to cancel the darn thing!! I'm so fed up speaking to your lying call centre agents. Please get me someone high up that CAN help me.