Telkom ruining my credit score

I have lte wifi and i had telkom agents come into my home for a promotion for home Fibre installation and I signed up and they said they will take care of paper work of upgrading me and activating my Fibre and they came to install Fibre unfortunately I needed to activate by calling Telkom and that was never communicated to me by walk in agents and that wasn't the case I continued using LTE and billed for LTE until I started receiving threatening sms that I owe ,I called telkom and they saw my Fibre never worked and I wasn't supposed to be billed for something that never worked they disputed and said after 48hrs I must call to cancel and I did but now I'm being handed over for something that never worked so Telkom is charging for me something that is not working and called them and notified them