Arreas on fully paid account

I had an account with vodacom but my device was broken so tge insurance said they cannot fix it and they could not replace it. So i decided to settle tge account in December last year so i asjed for settlement letter abf i paid the settlement amount then i went to Canal walk vodacom store to email tge cancellation documents to the cancellation department. But now on my bureau it shows that i have outstanding amount. I logged the incident and got the reference number anf they saud i will get back feedback within 7 days but until today they just sending email and sms from collections department whrn i call they give me numbers of different departments but no help. Its really affecting my credit score and the consultant that was busy with my case does not reply on my emails now