Backlisted for no reason

Vodacom gave me over to VVM Acc NM085772 , whom I had to pay 932.33 on 10/12/2020 outstanding money to for an contract that was incorrectly upgraded and cancelled.

VVM was unable to tell me the reason for the outstanding money nor were they able to supply a detailed invoice for months,

I went to Vodacom in Mall@Redds who said that the account is clear and that it would have been impossible to convert to a Pay as you go if not settled.

I eventually payed the money to avoid getting black listed but after payment I was still blacklisted.

I called VVM whom said that I now need to sort with Vodacom but Vodacom does not have competent staff that can assist.

Please help.