Health insurance denying claim

Greetings, wanted advice with regards to health insurance that i had taken for my father. The claim was denied in 2018 and when approached the Sales Lady who had sold me the insurance did advise that from next year it would be covered as the disease was not disclosed at the time of inception of the policy. I did check with her and she advised that it would be covered from next year onwards. I have this written in my Whatsapp conversation with her. Further to this, when my claim was rejected in 2019 again. i rechecked with the sales team, the sales guy and the sales team leader both confirmed in an email that it would be covered from 2019 as the wait period is now completed. The claims team have rejected and advised again that as i had failed to disclose this condition at inception and after 1 month they went further ahead and cancelled my policy. My annoyance is the sales team have repeatedly agreed to being covered whereas the claims team have cancelled it. my question is in 2018 when i had put a claim that only rejected the claim but did not cancel the policy, when i was informed by the sales lady that it would be covered from 2019 i did my renewal on time. They accepted it. now the 2nd time after 1 year wait i did apply for claim for the disease and they rejected and went further ahead with cancellation, even though i have written email and whatsapp conversation with 3 staff members confirming my coverage. What are my rights. I have approached their grievances cell and have been waiting for a quite some time now