I am about to make my final garnishment payment this week- and just realized the collection agency's license in the state of Michigan lapsed in 2009... what can I do at this point?

They have a judgment against you OR this is a private agreement you are calling a garnishment?

Assuming it's a judgment, who got the judgment against you? The creditor or the agency?

If you think they acted illegally, report them here - Check and See if a Collection Agency is Licensed in your State-All States listed to Check Collection Agency License-File Complaint Against Collection Agency