Credit profile impacted negatively by an error caused by hammond pole

Hammond Pole Attorneys provided me with a settlement letter last year in April and I paid the amount reflecting on the letter in full. It was regarding my woolworths credit card account that was administered by them. To my surprise they are claiming that the amount provided was given an error and I still owe Woolworths.

This matter has been investigated and they arrived to a solution that I don't have to pay any additional amount. However to date my credit profile is impacted by this account.

Please help clear the outstanding amount as the error was done from your side and update my credit profile accordingly.