Outstanding amount that can't be explained

I got notified of an outstanding Telkom account that just got added to my credit score. I called Telkom to find out what this account was for and when I opened it.

The only account I have ever had with Telkom was for a modem back in 2014 which I paid off. I called Telkom to enquire and the agent also couldn't explain this sudden new account with an outstanding amount of R600 odd. He gave me a reference number and said someone from billing would call me... I have been waiting since!!

This is messing with my credit score so I urgently need it corrected!