My husband's wages have been garnished too much, how do we get the money back?

A couple of months ago, my husband was ordered to pay for a thousand dollar hospital bill via wage garnishment. He is payed weekly, so they have been taking between $150 and $250 for the last 5 weeks. At last count, a little over $1300 had been garnished. My husband thought that was too much, so he stopped by the court house today and asked for an explanation. He was told that because the money is going to a collections agency, the court house first receives the funds from my husband's employer and then sends them on to the collection agency. Only when the collections agency reports that all of the money has been received will the garnishment stop, and because of the delay in getting to the collection agency, more than the specified amount has been garnished. The woman was very curt, and my husband was not given an explanation as to when he would get the money back; if he would have to go after it himself or it be sent to him; or who he would actually have to procure it from (court house or collections agency). I would love some advice on how to proceed here, as the garnishment has affected us dearly and I feel very violated and as if none of the parties involved are particularly concerned with us getting *our* money back (the extra $300), which I feel they never should have been authorized to take. Being that the court house is involved, I'm sure its a legit practice, but for the sake of argument, is it possible that someone has made an error and is not owning up to it?