A new assembly bill (AB1407) goes into effect July 1, 2016.  The bill was approved unanimously in the Senate and Assembly and signed into law by the governor. The addition to the Family Code makes it possible for family law Judges to order a cell phone carrier to separate the cell phone number of the requesting party and children, as well transfer as the associated rights and billing responsibility to the requesting party.
The reasoning behind the bill was that victims had no way of separating their own phone number from that of the abuser, meaning their call history could be seen, the batterer could place restrictions on the phone plan, or sometimes even locate the victim through the GPS on the phone.  Once the bill goes into effect next year, victims can obtain an order which will allow them to continue use of their cell phone number, access to contacts, and will save money by not having to pay for an additional phone and phone plan.
If you or someone you know is a victim of domestic violence, there are resources available.  What is required is different for everyone, so be sure to seek out the assistance you need.