Can this be sent to collection?

[GodsFist]

When I was married, my wife had a security system installed and signed a 3-yr monitoring agreement. We separated within the first year of that. She moved from the home and out of the area, so that company could not provide her service. They are now calling her demanding payment... I told her to have them contact me since I still lived in the home, but just don't want the service. Can they send this to collection even though they cannot provide her service where she moved? Or, is she no longer liable if she notifies them that she has assigned the contract someone else?