Missing estate of R3000 000.00 ignored

My 82 year old father has been struggling for 18 months to find just over R300 000.00 that is missing from my late mother’s estate. Tons of calls, emails, bank visits and he has been ignored, messed around, **** to and received the worst service ever to try locate this missing investment!!!! My mother was a long standing and loyal Nedbank employee for over 25 years in the home loans which makes this even more shocking. I AM NOW BEGGING management to step in an help my father !!! He’s been shunted around for over a year and treated with such little empathy in this situation. This is a huge amount of money and the attitude towards my father has been just terrible.