Garnishment is a legal process served on the employer, not the employee. Actually the employee has no recourse unless the alleged uncollected debt has been paid at which time the employee gives proof of this to the collection agency. Also, garnishment has a pecking order, and federal garnishments, e.g., for back taxes, will go the head of the line. Hope this helps.
The one way to end a garnishment is to negotiate a payment plan with the collection agency (or, preferably the organization that sent the bill to collection...the collection agency takes a fee and makes the fee higher) and it will not then come directly out of wages. Hope this helps.