Refuse to reveal cancellation penalties, until you cancel

I want to cancel my 2 year Telkom contract, due to it being double the price of what MWEB charges for a similar package. It has 6 months to run until expiry, but Telkom billing refuse to disclose what the cancellation penalties are. They say we will only know what they are once we have put in the request for cancellation. How ridiculous is that! So I cannot make an informed decision, as I don't know whether they will bill my hundreds, or thousands of rands.... I think they do it deliberately so that you won't cancel.... Does anyone know where I can get the information on the cancellation penalties?