Exorbitant Telephone 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. My telephone number is ***, ID number ***