Shocking vodacom service

Hello.My name is Tracy.I have had the most unprofessional unsuccessful and frustrating experience with vodacom.My mom is 85 years old.Last February i downgraded her contract.Due to a vodacom system error they neglected to downgrade my mothers contract.I recently uncovered this vodacom error when trying to assist my parents in getting their affairs in order.The result of vodacoms error is a ten thousand rand loss to my parents which they cannot afford.Despite my repeated attempts ,both telephonically and on email,with numerous vodacom employees in different departments ,vodacom has yet to downgrade their contract and reimburse them the ten thousand rand which they have acknowledged is owed to my parents.I'm mot sure where to go from here to assist my aging parents.