Widow can not get Lifecover paid

My husband died on a car accident 15 Jan 2021. The only thing he left for me and my son was a life cover by FNB bank. I spent all my time trying to claim the money and FNB did not pay. I was told to submit a letter of Authority to the bank since the was no beneficiary nominated and police report. They change the story and wanted a letter of execution that require money. The only money i got was for funeral. My child can't go to school because i can pay school fees and i do not have any place to go.