Cashless hospitalization rejected - Manipal Hospital not in network list

I have a health insurance policy from Max Bupa with sum insured of 15 lakhs. Last week, my sister had to be admitted to Manipal Hospital in Pune for dengue fever. When we tried to get cashless treatment, the hospital said Manipal Hospital is not in the network list of Max Bupa. But when I bought the policy, the agent told me that Manipal Hospital is covered. Now I had to pay 6 lakhs from my pocket and I am trying to get reimbursement. Has anyone faced this issue? What should I do? Can I file a complaint somewhere? The TPA is also not responding properly to my calls.