Paid off settlement amount and pay another one. Where have you ever seen such

I am currently having the worst experience with this Direct Axis. I have requested a settlement letter which they gave to me on 12 Sept 2020 where i was to pay a total of R23 962.77. The amount was paid in full within the stipulated period indicated on the letter and to my suprice, almost two weeks later im told i have an outstanding amount still to be paid. I called and sent e- mails requesting a logical explantion to this effect but i am not getting answers, instead they sent me another settlement letter indicating payment of the additional amount while at the same time im being sent from pillar to post with my quiry but no one tells me what that additional money comes from. I have even submitted a complain to ombards because even if i pay that money i want an explanation. By end of this week i wil go to the press and expose their incompetency at my expence and maybe then i will get to understand what that additional money is for. I will not live this matter until its closed.