Exorbitant WiFi account

I have an account with Telkom and on numerous occasions I enquired about my bill they promised to call me. Numerous times when I went to their offices they promised to cancel the bill because they also agreed that it was not my account. I proved to them that my account average was in the region of R500 per month and they said they’ll fix it. Last week I was called by someone who claimed was from a debt collector informing me that telkom had handed my account to them. How could this be possible despite promises to fix the account and come back to me.