Go to the clerks office at divorce court and ask them for a form to stop the garnishment. As long as there are no arrears you will be able to get it stopped by filling out the form and paying the court their filing fee. If you are behind you need to enter a plan for payment of the arrears. Any lawyer can do this for you as well if you can't figure out what to do. The lawyers office will charge for their time and charge a runner fee and charge the court fee as well.
There are many factors that can affect how best to handle this matter and the best advise is to hire an attorney immediately. Unfortunately the advice above is a guess that is based on very scanty facts. Circumstances of all sorts can change the ultimate answer you need. If you want to know how best to handle the situation, make an appointment with an attorney and get good solid advise based on more exact facts. The money spent might give you the peace of mind you need.