Struggle to update a paid up account

Hello Peter, I called creditworx for a settlement quote on the 29th Jan 2021. Ms Nicole helped with that and then emailed it. Few days later I paid the whole amount. I then emailed proof of payment and received a reply with it will be updated on their system. Now the same company is sending me sms about R300 that I owe. I am not sure where is that from. What is the point of requesting a settlement amount and then the account keeps coming back. Why is this company acting like they do their best for one Not to pay up? I called their offices couple of times and I got they are still updating. I don't have the R300 they are asking that is why I requested for settlement quote When I had the money.

Thanks