International roaming and sim card closure

Cell C has disconnected my mother's international roaming and closed her sim card without her consent. After numerous calls, emails and complaints to the so called customer service, the only solution they give is to call the call centre. They have no understanding of the frustration and expense it takes to call internationally on numerous occasions and get no assistance. There is no network for her to dial the star numbers they keep telling her to dial. Their customer service email and complaints email is the same and there has been no resolution to date. They make empty promises to resolve the complaint. Why does cell c have international roaming if they refuse to assist their international clients. Dealing with the agents is draining and literally sickening. My mother has had her contract with cell c for 17 years, always been a loyal customer but this is how they are treating her. They continue to deduct premiums for a non existent service. If anyone at cell c has any respect for another human being can they please help my mother. She is alone in another country with no network!