Vodacom billing mistake causing me a lot of issues

What an unpleasant experience. Been trying to open a new contract with vodacom for the past month but it keeps getting declined because apparently we have R1 areas from years ago. Now firstly that amount was a debit order, I went into my bank account history and did not once have insufficient funds so the R1 is clearly a vodacom billing issue. Secondly, not once did vodacom let me know of this arrears amount I had to find out about it when I realized my credit score is badly impacted by this R1 Vodacom did not debit correctly. Then I have been contacting them and trying to pay this R1 and everytime they tell me it is sorted but the next time I check it is still there

It is one thing that vodacom cannot sort out their mistakes and that I cannot get a new contract with them but this is impacting other aspects in my finances.

This needs to be sorted out asap and I want proof this time and they need to correct the history of this that is impacting my credit score.