Room rent limit causing claim deduction - need advice

My self was hospitalized for 10 days for knee replacement. The total bill was 18 lakhs. My health insurance policy has a room rent limit of 2000 per day, but the hospital charged 15000 per day for the room. Because of this room rent capping, the insurance company has proportionately reduced my entire claim and only paid 5 lakhs. I had to pay 12 lakhs from my pocket. I did not know about this room rent proportionate deduction clause when I bought the policy. Is this fair? Can I challenge this? Should I upgrade my policy to remove room rent limits? Please advise.