Sadly, there is no such thing as "giving it back to the bank".
As I understand it, the debt remains, as a result of the signed "contract".
Some years ago a friend bought a house for $180M. Being unable to pay, because of illness in the family, he left the house and moved into an apartment, telling the bank that he could no longer afford to pay. In time, the bank took back the house, sold it for $130M, and left my friend with... not only the $50M loss, but fees, charges, and interim maintenance of another $20M, an actual total responsibility of more than $70M debt (plus interest) and nothing to show for it.
I hope that someone here can give good advice, or point a direction. In any case, "letting it go back" may not be the best choice.
Not much help here, but a little more about the actual plan.
Mortgage Plan 
