What if a creditor wont give there address for a cease and desist letter?

If it's a third party company you can tell them to cease and desist contact over the phone they have to accept it verbally but most of the time they will tell you it wasn't in the notes. There not going to give you there address if you tell them that you are sending that letter as they know they are not going to be able to contact you. Also remember that if they sell it to another company you will have to send that company a different letter so it starts all over. I would call them and ask them what there address is so you can send them a payment and just send a certified letter to them instead of the payment if they give you problems tell them you are sending the payment certified so you have doent of them receiving it. Also remember that just by sending this letter it doesn't stop collection efforts and sending the letter will probably make them proceed with legal action faster than if they were calling you as they now know you don't want them contacting you so be aware that you will probably be taken to court and have a judgment placed against you.