Vodacom charging for imaginary "Content Services"

Vodacom just starting adding "Content Services" to my bill and I hadn't noticed for a whole year. When I called customer support to query what this item was, no Vodacom employee can tell me what it is. They just say it's a service that I "subscribed" to on my mobile phone. Some support agents said it's for "gaming services", and I never play games on my phone. This cannot be a "subscription" fee because the amount every month is different. What else besides voice air-time and data do I need to pay for?

No support agent can also confirm what service the charge is for. What is the name of the service, which website? What application did I use? How is the charge calculated? Per minute? Per what? Vodacom are charging for a service that doesn't exist. I have been charged over R1600 over the course of a year. Finally, after complaining on social media, an agent credited my account of around R300. That's only 2 or 3 months out of the 13 months. That's Vodacom basically saying "yes, we made a mistake with your billing, but we can only refund you under 20% of the money we took from you".

I require a refund in full, otherwise I am cancellling my contract at the end of this month.