Blacklisted for loan paid a year ago

Due to unemployment I defaulted on my payments. African Bank sold my account to Norman and Bissets. I paid the account in full in May 2016 but credit profile shows the amount as owed.

I called African Bank for assistant. They asked for the proof of payment which I have since sent to them in June this year - no response.

I have called them numerous times. Their consultants do not seem to understand what it is they should do with my query. I spend 30 minutes or more on the phone explaining and then I'm told firstly, that it is not an African Bank issue, that I should call Norman and Bussey. Norman and Bissets already confirmed; because it was African Bank that made a default on my account, they aren't able to contact the bureau to assist. I am then told by African Bank that an investigation needs to take place and that I will be called back. This was beginning of July, 3 calls later, no call back. No ability to improve on my xredut profile. They are seriously stunting my growth abd they don't care. Transunion shows this amount as owed. I want this fixed asap.