What good is a Trust and a Will if they can be overturned?

One day after my Loves death, one son called me and asked if there is a Will. I said yes and I would appreciate giving me a bit of time here to grieve. He is named in the Trust. I am sure it is the other son's way to see the Will and begin his fight. The second son was intentionally left out of the Trust. Now I am being told they can freeze my bank accounts. I am also told that the home my Partner and I occupied and is now mine, can be overturned. The trust and Will were signed 2 years before he passed. He was in sound mind even up to the end. He never signed anything once he was on Hospice. I would not have allowed that. There is a possibility based on how my Partner handled his annuities that they are all going to me. Again, what good is a Trust and Will if the son who was disowned by his father IN WRITING can change things?