Care Health Insurance - Claims rejected

Dear Sir, This policy has been started in year ****-**. At that time we have disclosed what all complications are there with the Insured person. I have paid * premiums till now from FY ****-** till FY ****-**. The insured person got sick in March. She has been taken to doctor and doctor diagnosed her to have low blood level and asked us to admit her in hospital for blood transfusion. Till now in last past ** years the insured person has not had any such kind of issue. I made a claim to insurance company. But the company rejected the claim citing reason as we have not disclosed Anaemia. This is a sudden issue as Insured has no record of transfused blood before. How can person disclose such issue which was not there at all. Doctor has also confirmed that she doesn't have issue of Anaemia before and no record of blood transfusion. She was admitted with issue on Hermia in **** and at that time as well no blood transfusion took place.Team, please help to resolve this issue as it has already been delayed.