Telkom won't let me go

I don't understand why telkom will not allow me to cancel my service. My 5gig data sim contract ended on 24March. From January they have been calling me to upgrade and on all calls I have been very specific about canceling and not wanting an upgrade. I get calls 3 or 4 times a day. I keep saying the same thing and now I've started blocking them and not answering. The only problem is, now they gave reloaded the data, I don't want it. I have unlimited data with rain, I said this on the calls as well. When you try to call the call center it hangs you up saying they've sent me the self help sms which doesn't give me the option to process the cancelation. On the app, same story, when trying to cancel it takes you round in circles and never actually goes ahead with the cancelation. I no longer need this contract and don't wish to upgrade. What are my consumer rights here. I have said cancel from January yet they're still loading the data which means I will be expected to pay again for the service which I do not want. I need serious help. I don't caregow small the amount is, I don't want it anymore and my wish should be respected