Car Repo

I bought a car almost a year ago, in guam had to leave to come back to the states and I signed the car off to my wife's cousin ( this was not done at the bank we signed and had a verbal agreement that she is responsible for the vehicle, payments insurance everything etc etc )
the vehicle was reposed and now the bank is trying to collect 4 1/2k from me.
Is this my responsibility or does this fall on her cousin?

The bank has already gone to a lawyer about this.

And now they are contacting me about it.

What do i do about this?

I don't have the document but my wife was their and is a witness to the paper being signed, and the verbal agreement we had.