Unable to contact granddaughter in another state?

My step-granddaughter lives in Texas with her father and stepmother. She visits every summer and every other Christmas holiday. My daughter in law is not able to contact her daughter during any other time of the year. The custody agreement in California states that she is able to talk to her daughter at any time but the non-contact issue started 3 years ago when they moved to Texas. My granddaughter was able to use a friend's phone to talk to her mother, but since they moved to another school district, all contact ended. They moved because the school had to report the stepmother for physical abuse and child protective services visited the home to investigate. We worry about her because of the verbal abuse and her father not stepping in so he can keep the peace between him and his wife. What can we do?