Phone plan

Who usually gets to keep the phone plan after divorce? My mom and I are the plan with her ex husband. She owns 2/3 phone numbers on the plan. If we leave it, we would lose out on the plan currently that technically no longer exists anymore. Is there a clear cut answer to who would get to keep it? I’m not able to leave the plan yet pending mediation, and was looking at other plans but there is a $50+ difference per line compared to the current one we have.