Vodacom cancellation of contract and extra charges

I upgraded my data sim card last July 2020 to 50 GB. 2 days later we decided to rather get in uncapped fibre. Vodacom said they would swop our data package for the fibre if we took the fibre with them, which we then did. They have been charging us for both the upgrade and fibre since July. I have queried this twice with them with no success. They have been charging me R300 every month for 6 months =R1800. ****************. Very frustrating.