Unpleased old woman

We are really not happy with African Bank. Our father passed away in 2020 and they notified us that he had an insurance with them. They needed the executor which is our mother who is old and constantly sick. We arranged for her to the bank and she completed the forms before she was sent back and forth several times that was from 2022. Now this year in January after submitting her details and other forms which are duplicate of what was previously sent they promised the claim to be paid in February before the 10th. It's now May and no payment was done. It's killing our sick mother and its also a battle for us as we are not staying with her we cant go home anytime to take her to the bank. Now she is constantly sick and thinks that's what the bank are hoping for her to die so that we can forfeit the money our father left for her. We are talking about an old woman who is 75. Please assist our mother she only want what is due to her. Our father trusted this bank and now they're failing his wife. Are we supposed to have business with them after such treatment of duplicate after duplicate. We sent emails we went inside the bank they scanned and sent emails as well but no help was given. We lost hope and only hoping our mother doesn't die in the process. Please help us to get this matter resolved.