Can I file a lawsuit against a creditor?

Yes. You should send a letter to the creditor and request him to remove the wrong information from your credit report since it's a FCRA violation. Threaten to file a lawsuit if the creditor doesn't correct the error.

Yes, it is an FCRA violation. But are you sure the debt is not yours? You can ask them to validate your debt in writing as well.

If you file a lawsuit, you'll have to bear the attorney fees. So, it's better you dispute it with the creditor and the CRAs. If the creditor doesn't do the needful, then you can go ahead with the legal procedure.

Definitely an FCRA violation, send an official mail to the creditor and ask him to remove that wrong item from your report asap.