Aditya Birla Health Insurance — Cashless claim rejection

I have a 1 year insurance policy for my father aged 80 years(bought on Feb 2023) with known and declared case of hypertension. Currently he is admitted in a hospital with chest congestion problem, the insurance company has rejected cashless claim by referring to an older 2020 general medicine prescription where doctor had mentioned IHD, so insurance company says I have willingly not disclosed heart disease while buying the policy, but the fact is that we were never told by any doctors(not even the current treating doctor) that the patient had ever any heart disease and need any treatment.So how would I know as a common man that the patient had any heart disease.Also this 2020 prescription has been shared with them by me only, if I had to hide anything knowingly then why would I have shared this document, I could have said that I dont have any old documents, doesn't this prove that I was never aware of any heart problem for my father and even till now he is not having any heart problem.So I feel they are incorrectly rejecting the claim with a wrong reason.