Student loans

My son's defaulted on his student loan finally caught up with him and ConServe is threatening a wage garnishment on behalf of the Education Dept. He owes the money and is finally back on his feet. He can afford to pay it off in a lump sum. The problem is his current job takes him out of the country and out of communication for long stretches at a time. He tried doing an electronic transfer but the numbers are messed up and the payment is not going through. I've been acting as a go-between trying to deal with ConServe and getting him the messages. He plans to go directly to his bank when he returns to the states mid-November. I do not think ConServe will wait that long, they've already delayed it a month. My question: Once the garnishment is in place, how difficult is it to get it stopped?