Random invoicing

I stopped using Rain in 2020. They stopped charging me in 2020. In 2023 they started invoicing me again because I supposedly haven't cancelled my subscription. Now I'm trying to cancel my subscription and they want to charge me R999 for the cancellation. Firstly, you cannot just randomly start charging someone with no communication and re-activation or whatever reason. Secondly, no one can give me documentation that I've agreed that the contract will be charged to get canceled. There is supposedly no contract, so how can you charge someone for something not agreed upon? Also, it's supposedly post-paid, so if you don't use data you don't get charged. But I'm not using data now, why am I being charged? Their system has problems and the client needs to pay for it.