Garnishment and off-set taxes

I have been dealing with DCS now for about a year on a defaulted student loan. Last year I was contacted at my job by a customer service rep, and informed that my student loan had been placed with them for collection, and they would like to make a voluntary payment arrangement which I was open to, but the terms of the payment arrangement were not something that I could handle, due to the fact that I do not have a checking account and I have not had one in over 10 years, the rep informed me that I needed to get someones Checking Account information so that I could make the payments that were discussed because thats the only way that the payments would be accepted. I didn't know what else to do and the next thing I know my wages of a little over $900 a month were being garnished for a $150. Then I have received a letter saying that my taxes for 2011 will be offset....not trying to sound like a cry baby, I don't deny the debt, but I need my income taxes...bottom line, and I really can't afford to pay $150 a month either, I have two kids and we all have to eat. Does anybody know of anything that I can do? I did ask about an option out of garnishment status and they said I would have to make 6 consecutive voluntary payments of $98 a month on top of the $150 that was already being taken....needless to say I can't afford that...Please Help.