Rain disappointment

I am really disappointed in rain provider. The whole of last year we had 4g and it worked just fine and we paid R479 for it or the whole year and amount never changed. 19 November 2021 we decided to get 5g and paid for it in advance as per the terms. We didn't know that we would be paying for both 4g and 5g. After 2 - 3 days of using 5g we which wasn't working at all because it kept having network problems we decided to switch back to our 4g. On the 19th December 2021 we decided to cancel the 5g because it just wasn't working for us and we disconnected the simcard. Which was in time so that we don't get charged for the December to January period. They only came for collection in January 2022 amd my invoice is R978. How did I get charged so much if they say my prices are standard?where is the other figure from