Your wages are being garnished. You understand the debt and you don't deny that it exists. You're not contesting based on the fact that you think it's inaccurate. That doesn't mean you can't contest the garnishment at all.
For instance, you may be able to put in an exemption claim saying that you can't pay your standard living expenses because the garnishment takes too much of your monthly wages. It's a hardship that's putting you in a potential dangerous and unhealthy position.
Maybe you need 80 percent of your income just to pay the rent, keep the heat and electricity on, put food on the table for your kids and make sure you all have adequate clothing and other necessities.
However, the garnishment is taking 25 percent of your income. It doesn't prevent you from paying all of those bills, but you clearly have to pick something to miss each month.
This is just a hypothetical example, but you can see how problematic a garnishment could be and why you may have the right to challenge it. To do so, you will need to prove what you earn each month and show all of your unavoidable expenses. The court can then overrule the garnishment if it sides with you.
When debt mounts, creditors sometimes use all of the options they have to reclaim that money, but the point of a garnishment is not to put you and your family into poverty. If you feel like it is unfair or unjust, make sure you know all of the legal rights that you have.
Source: Credit Cards, "Steps to contest, end wage garnishment," Tanisha Warner, accessed April 07, 2017