Vodacom Charges You For a Service But Does Not Let You Use It!!!

My fibre account had gradually increased since I finished the 12 month contract as I was on month to month. I told Vodacom that I want a better deal on the same line as I was not prepared to pay the increased subscriptions. My account fell into arrears and they LOCKED my router which prevented me from using it. The worst part is that they are stilling billing me for the months to come even though I cannot use the fibre service. Is this legal? How can we be expected to pay for a service and they are not providing, I am on a month to month contract. I then asked Paballo from Subscriber Collections to cancel my line as I do not want to be further billed and she said that the arrears must be paid first. So now I must accumulate monthly billing charges before I cancel? Is this legal? I am not in a contract! Paballo insisted that I have been allocated the Fibre and therefore I must pay for it, so I asked her, can I use the fibre line then? She said no because they locked the router. So then I asked her, how can I pay for this if I cannot use it, she goes back to saying because it was allocated it to me. I then say unlock the router so I can use it, she says no, not until the arrears are paid? What kind of logic is this??? Surely, this is not legal to charge a customer for a service that you are preventing them from using.