His last will means nothing

I had a life partner who was diagnosed with Stage 4 Cancer. We new that there were not much time left for him. We contacted ABSA, as he had an old will there, but wanted to make a new will, where his sons will get the bulk of his Estate. I contacted the lady at ABSA, and she said that if he comes in, and sign the application for a new will, that will stand up in a court as his last will and testament. We went in, he signed and they took note of his last will, needless to say, ABSA did not take that as his last will and testament. They are using the old will where the mother of his sons gets everything. Thanks ABSA for not caring enough for what his last will and testament was. I have tried many ways to get them to obey his last will, but it is like walking into a wall. Why did they tell him, that if he signs the application, that will be used as his last will and testament. Doesn't the right hand now, what the left hand does?