Credit History damaged by incorrect billing

I used to be on Virgin mobile contract about 3 years ago before I switched to pre-paid with another provider (a very normal thing to do) but unfortunately by cancelling my contract somehow my final payment did not come off and my credit history has been impacted ever since. <br> I spoke with a Virgin call centre staff now (ref VRSN***9) and the lady told me that before my contract ended I changed my debit order to cash and didn't make final payment. I don't recall doing that as I wanted to cancel my contract. I then did settle the R244.07 with a debt collector (not because I acknowledged wrong doing but to clear my credit history) but I think even that was a **** as the collectors never contacted Virgin mobile to say I settled my debt. I researched the collectors number ***) and it appears to be a ****. I therefore cannot contact them to ask for proof to be sent to Virgin mobile.<br> <br> I therefore have no idea how to clear my credit history. Hopefully Virgin staff can contact me.