Turned in my truck

CA, My husband and I bought a truck about 18 months ago, but since then he has taken a significant pay cut so we can't afford it now. We called the financing company and didn't wait for them to reposses it, thinking that we were doing the right thing. Before we actually turned in the truck, I called and talked to a bankruptcy lawyer and he told me that we could file on the remainder of the balance after it is auctioned, which was part of the deciding factor in giving the truck back. After we turn in the truck, I get a call from a manager at the financial institution who tells me we can't file bankruptcy. Was the lawyer correct..or the financial institution.