Cashless hospitalization rejected - Max Hospital not in network list

I have a health insurance policy from Max Bupa with sum insured of 10 lakhs. Last week, my brother had to be admitted to Max Hospital in Bangalore for severe pneumonia. When we tried to get cashless treatment, the hospital said Max Hospital is not in the network list of Max Bupa. But when I bought the policy, the agent told me that Max 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.