bad costumer service

My sister had a contract with cell c. Last year she she lost her job and could noy pay her account. She was payed some money and she decided to settle the contract after her phoned was switch off and because she was phoned by the legal department. She received a settle amount and paid it. She received a call from the legal department to inform her she is still owning. My concern is no one know or make notes on the system that indicate what they did for next to see. My sister cant go through this any more for she cant pay this amount they want cell c to pay. It seems cell c has a bad customer care program and the agents don't keep record. For myself after my contract ends I moving to a different service provider cause myself lost faith in cell c