who can I call if I think someone is trying to scam me because of my loan?
Stay away from anyone you feel is trying to take advantage of the situation and contact the Default Resolution Group.  The Default Resolution Group can help you get your loan out of default for free
There's one more thing I'd like to say about loans. Is there a tax benefit to choosing an income-driven repayment plan?
Yes you might have to pay taxes on the amount forgiven especially if you are making payments of $0 per month.