Cashless hospitalization rejected - Columbia Asia not in network list

I have a health insurance policy from Max Bupa with sum insured of 5 lakhs. Last week, my mother had to be admitted to Columbia Asia in Pune for emergency surgery. When we tried to get cashless treatment, the hospital said Columbia Asia is not in the network list of Max Bupa. But when I bought the policy, the agent told me that Columbia Asia is covered. Now I had to pay 2.5 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.