Vodacom double payments

I was halfway through a two-year 20GB Vodacom Data Price contract when I app**** to replace it with a Fibre Broadband contract. The fibre was installed, and became operational on 17th January, 2020, from which time I started to pay the slightly higher fee for the new service. The original charges continued in addition, however, and the months since then have been a long story of communicating in person, by phone and by email with people in Vodacom. In the latest conversation I was told that the original contract cannot be 'replaced ', but only terminated on payment of a fee, a sum greater than the amount outstanding on the original contract. It seems that different departments do not communicate with each other in respect of a particular client. Irrespective of the long complicated history of who said what I believe that Vodacom should not accept a new contract in a case like this unless they are prepared for it to take the place of the original one, which obviously cannot now in practice be used. I am now put in the position of paying for two contracts, but receiving the benefit of only one. I do not believe that this approach meets the principle of treating the customer fairly.