Welcome and congratulations on the deletion. Your scores should see a nice boost.
Do you have a copy of a receipt or cancelled check for the account that was already paid? You will want to find this and send copies to the company stating it was not paid. If you paid the OC then contact them and have them send you something.
Otherwise, you will have to sue if they do not rectify this.
myFICO is the consumer division of FICO. Since its introduction 20 years ago, the FICO® Score has become a global standard for measuring credit risk in the banking, mortgage, credit card, auto and retail industries. 90 of the top 100 largest U.S. financial institutions use the FICO Score to make consumer credit decisions.