My estrange husband trade- in my car to a dealership without the title,?

the title was and the regestration in my name only i was the primary owner and he was only a co-signer, they did the transaction without consent or permission, now they continue to call and harr me for me to give them the title can they sue me for me to give them the title after the transaction that was done bewteen them both is final this was done since last year august 2008 and i still have my original title when i went to them in the begining they told me that they can not show me any paper work because i was not the customer