This is often nothing more than a smoke screen to get you off the phone. I would focus the conversation on “selling their house” rather than “listing” their house. After All that is what they want. 

Seller: We are not ready to list our house.

Agent: no problem, you do want to sell your house, correct? (let them answer)

Immediately go back to the next question on your script

To get my entire script book for free Click here