Rejected Funeral claim

My mother registered my late Grandfather for funeral plan policy, but the claim was rejected because He's not the Biological father the brother of her Biological father. What happened is that, my grandfather raised my mother, and She registered him as her Father since He raised Her. So when she was claiming, they told her to right an affidavit, and she wrote that He was her father's brother,and she was told that no deduction was made. At this point we're devastated and have no money to do the burial, please help us resolve this, because we feel ill-treated