Filing bankruptcy, quitting your job, earning less than min wage x30 hours a week, or paying off the debt will stop the garnishment. Otherwise, you are pretty much stuck with it, since the lawsuit and the chance to contest the debt has come and gone.
You can go to court and ask the amount being garnished be reduced from 25% to 15% if you can show how it is a hardship: many judges will do that.
One of the documents served on you at the start of garnishment is a "Request for Hearing." Fill it out, go to court and ask for the garnishment to be reduced, and see what the judge says.