Why must we pay more?

As part of a way to recover financially from Covid I pay all my debts so I can clear up my debts and credit record.... I have fully paid my account as arranged which is also on record that after a certain payment I won't be owing the company a cent and after the last payment went through I called to request for a paid-up letter but to my suprise the consultants in MBD are saying I'm still owing MBD. I requested an eplaination on why am I still owing the company while I had requested to pay all the outstanding amount which was paid via debit order and no one is able to explain to me and everything was on record as they say everytime...I have honuored my arrangements with the company and my request with the company to clear my debt and send me a paid-up letter. I know I am not the only one having the same problem with this company and this company is the reason many of us blacklisted due to thier charges which they impose on us they wish.