Experian false information as they do not update

I have a huge complaint today. After numerous mails to the customer centre and to the company I have had the loan with which is paid up and confirmed as such on their side it is still listed on Experian as open and in arrears. They just simply do not answer back or make any effort to communicate or rectify the situation. I have send proof that the Loanzie account listed has been cleared. Send them a paid up letter and everything and yet no joy. I have been battling with this situation since September 2022 and it reflects negatively on my credit score due to the fact that nobody there cares to do their work. I have had seven people read the mail with just no reply. This is unacceptable!!!!!!!!