Can they contact your references-yes
Can they release info about the debt-no
The purpose of the references is for the creditor to get in contact with you if they havent heard from you....but you say you have been in contact with them, so I dont see the need for them to contact references.
On a 1st party contract, the Cease and Decist letter is not in your best interest...sure they MIGHT comply but they dont have to and they can view that as you not being interested in paying, especially on a secured debt that they can repo property for (your car).
However, you can tell your references to tell them to stop calling and send them a no call letter. They are not a party to the debt unless they cosigned.