Cell C does not provide a settlement letter after full payment and influences credit score.

I have paid up my Cell C account in July 2025. I received a settlement amount from the attorneys Shapiro Shaik Defries and paid the full amount. Ever since the payment has been made the attorneys provided confirmation that they paid Cell C. I have not received my settlement letter and my ITC still shows the outstanding amount which is now affecting my credit score. I went to the Cell C branch in Cresta more than a month ago and the lady sent all the proof to head office but nothin has changed. She requests feedback every second day but does not receive a response. I want Cell C to rectify my account and inform the credit bereau's immediately so that my ITC can be rectified and my credit score can be rectified. How difficult is it to provide a settlement letter?