DMC

I had an account with total sport that was handed over to DMC , so I did settle the account last year on the 06th November 2023 and I got the paid up letter now the account still showing in my credit report so when I ask them they said the letter is invalid I still owe them , this company is showing us flames the question is how do i get the paid up letter if I was not settle the account so when I ask them the account number to verify I'm getting the the different account can someone help us with this company