Inefficiency

I have previously had an account with DSTV multi choice that I have attempted to cancel multiple times. On the second attempt, I was assured by the operator that my account was intact cancelled. Shortly after I had transferred ownership of my decoder to my dad and had paid the outstanding balance which shouldn’t have been there in the first place as I had cancelled and was obviously still being billed. Note this was a good 2 years ago. I now get a call 2 years later from debt collectors telling me my DSTV account is overdue and has not been paid. Surely as a result this is now on my credit record?