Credit bureau fiasco

I recently learned that I have an unpaid amount from Telkom on my credit record. What happened is that when I moved, I gave a month's notice to disconnect the line and close the account. This didn't happen, in spite of my going to their shop several times in the next months. Eventually, they disconnected the line, and it took a while longer for them to reverse the charges for the 4 months that they had incorrectly kept on charging me for. They eventually sorted it out, ended up owing me R80 but I didn't have the energy to claim it. In the meantime, they had been sending my "not paying" to the credit bureaus but did not send the fact that they had reversed the charges and I did not owe them anything.