Cancellation of my contract

I will never advise anyone to have a contract with Telkom they did me dirty on my credit score it’s appears that I owe them R1800 on the other side they sent me an invoice saying that I don’t owe them I can’t even do anything because of Telkom appearing like I owe them and trust me when you call them they will act like they are helping you but they will never and because of that Telkom thing my credit score decreased with 19 point