Accidental/ Unnatural death claim

My policy has an accidental death benefit but when I submitted postmortem results, I was told that because the results came back as undetermined therefore I won't be paid for accidental death claim, because its not a valid answer. My uncle was 71 years and got missing for a year, the police found his remains burnt beyond recognition, how do we have control over what the pathologist right. Im disappointed because, I have even sent a complaint to old mutual and theyre not even acknowledging my email.