MRS refusing to take payments.

My sister had taken out a personal school loan a few years ago, my now husband co-signed. He has been getting harassed at work (he is the only one in the home working and we have 2 small children), they say they are going to garnish his wages unless he pays them $30,000 now. I told my sister and gave her the number since my husband was just a co-signer, so after being hung up on numerous times, she talked to someone. The woman was extremely rude and talked about a payment plan to which my sister agreed to start. The woman refused and said it was a common courtesy she was even speaking to her, and they would continue to go after my husband, the co-signer. We had looked up on my husbands credit report and it said the $30,000 loan had been "sent in request to the government" so Im really starting to think this is fraud, they refuse anything my sister offered to pay and eventually refused to continue talking to her about it. What can we do?