I'll fast forward and assume that you have attempted the suggestions that Blaison has provided below and that the lender has in fact sent you to collections.
You first have to determine whether your loan(s) are classified a recourse or non-recourse loans. You will need to find your Promissory Note, not the Deed of Trust, to check this out. The Promissory Note may or may not specifically state whether your loan is non-recourse, so for the formal definition please review questions 4-6 of the document found here:
If I was in your situation and my loan(s) were non-recourse I would be hard pressed to pay the collection agency a dime, and I would send them a certified letter informing them of the debt's non-recourse status and that if they continue to call you legal counsel will be contracted due to their harassment.
Sorry to hear about your situation. Collection people are worse, they just harrass people to get their money, they dont care about your hardship. But you have choice, try to do loan modification if you have the financial capability else you have to sell your house short (Short sale)
Did you get any notice of default(NOD)? After you get your 3rd notice of default then there will be a trustee sale where the bank is authorize to auction your house to the highest bidder.
Did you try for loan modification or short sale? These are some of options to avoid from foreclosure. You need to talk to an experienced realtor in short sale or loan modification so that you can fix this problem either by modify the loan or sell your house. Talk to a CPA or tax attorney for tax implication if you are planning to sell your house. Let me know if you need any help.
Certified Short Sale Specialist