₪₪₪ What are the IRS laws regarding discharged debt when the debt amount on the 1099-C form was incorrect?

I received a notice from the IRS regarding a discharged debt of $9,000.00. The letter stated I owed the IRS $1,400. My actual credit card debt was $5,000 (not $9,000). I never had a credit card with more than a $5,000 limit. I found out the debt was sold to another company and they almost doubled the amount of the original amount. How can I correct this mistake? Thanks for your help!