Vodacom service failure

I have cancelled my application with Vodacom before the service even began. I app**** in July 2019, they sent a router via courier, the service never connected despite several queries logged with them. The queries were never resolved. I had app**** for a month to month service and not a 24 month contract. After several follow ups on my queries, I ended up requesting a cancellation of service. I received a cancellation confirmation in August 2019. I am however still being billed for a service I never used. I have queried this with Vodacom on several occasions but no assistance. Please help!