Vodacom cancellation of service not working

18 months ago I contracted with Vodacom for a home internet LTE bundle. However, after a few months the LTE was very slow and I phoned Vodacom to complain and the consultant told me that the best option was to rather apply for Vodacom fibre, which I did. The fibre was installed and I have been using it and paying for it. However, Vodacom continued to bill me for the LTE data which I have not been using as I have switched to fibre. In November 2023 I phoned Vodacom cancellations to query why I was still being charged for a faulty service that i was not using. They said that they would follow up and get back to me. Never heard back from them. Over the course of the past year I have phoned Vodacom numerous times (I have record of most of these conversations), but each time I am told that it will be escalated, and someone will get back to me - however, that has never happened and I continue to be billed for a duplicate service that I never use. I would be so very grateful if someone could advise me on how to resolve this incredibly frustrating situation. Thank you - Rouen