C FIBRE are charging me for a service I haven't used

In 2017, I have consulted Cell C to get Fibre to my house, located in Dainfern Golf Estate. Checked on their website which showed that my house was covered by the service. After completing the foremalities, I was surprised to hear that Fibre is not yet in my area, and had to wait some months. After Vumatel completed infrastructure works in my area, Cell C Fibre confirmed to me that they were not selected as an ISP by Vumatel in Dainfern Golf Estate, and hence they cannot provide me the service, and with a clear cancelation email from them. Since 4 months now, I receive calls from Cell C collection Bureau, asking me to pay a charge of R300 for a data sim card that is part of the package, except that I haven't received anything from them. Every Monday I receive this call, I say I will not pay something I have not used, they answer they will escalate it, but nothing happens. At the opposite, each week the amount is increasing.

I've tried to call customer office, but my calls remain unanswered, and even the staff in the store they try to help, but no one seem to be able to solve it. Things now are getting worse, since Cell C have stupidely reported my case to the Credit Bureau causing me even more problems. The frustration is coming from the fact that I HAVEN'T USED THE ****TY SERVICE OF THEM AND WILL NEVER EVER USE CELL C.

I REFUSE TO PAY SOMETHING I HAVEN'T USED, this is total ****.