Family Law: Court order not being kept to

hi folks. im wondering can anyone offer advise on an issue please. my friend took his ex partner to court for visitation/access rights to his child. Part of the court order that was put in place was that his ex partner had to provide a valid contactable telephone number at all times. there has been an issue with the child in school in recent days and they contacted my friend the dad as they had been unable to contact the mother. they stil have not been able to contact the mother. my friend needs to contact her in relation to the matter but she has changed numbers again and he cannot reach her by phone. its parts of the court order that they had, that she provided a valid contact telephone number at all times in case there was any issues/emergencies with the child. is there anything that he can do to get her to give a contact number.