SARS is failing tax payers!!!

So it came to my attention that my mom owes SARS 60k. Reason being is because according to SARS she has been under taxed for 2 years. She gets inheritance monthly which is taxed. She recently got a job where she is also taxed. So she is taxed twice but according to SARS she is under taxed. The agent was unhelpful because she told my mom to go tell her employer that she is undertaxed. How is she meant to do this when she taxed according to her income bracket which she has no control over. SARS failed to tell her in advance about this and also failed to offer a solution. So every year she will be owing SARS 30k?? How I’m highly frustrated and I need an avenue or channels I can follow! It’s also the entitlement to her salary if she fails to pay.