Thank you for your follow up.
Unfortunately, may credit card companies have a clause in their credit card agreement (which most people never fully read) which allow credit card companies to pursue and lawsuits for damages in the jurisdiction specified in the agreement, which is usually the state with the longest Statute of Limitations and also with the laws most favorable to the credit card company's interest.
So, generally, the first step would be to obtain a copy of the judgment from the court that has issued.
If the personal information of the judgment debtor matches, then there are generally an option to file a motion to set aside judgment due to the lack of service, which would have to be filed in the court where judgment was issued and the judge will review all the records and evidence and will determine whether to set aside judgment.
If the judgment is set aside, then the creditor will have to start the lawsuit from the beginning by properly serving the judgment debtor and the pursuing lawsuit and if attorneys for the credit card are successful another judgment would be ordered by the court.
The second option generally, if the debt is valid, is to contact the attorneys for judgment creditor and to attempt to negotiate some type of settlement, so the judgment can be satisfied and recorded as satisfied, in exchange for the negotiated settlement amount.
I wish you the best of luck!