First submit the entire bills demanding for immediate reimbursement.
Let them reject the bills stating the reasons.
Then issue a notice through advocate making counter that the rejection is not legally valid.
Then make a complaint to Insurance Ombudsman and IRDI
Let this process continue for 6 months without spending an additional rupees.
After six months file Consumer complaint.
All this in good faith that the pre existing condition was not suppressed and policy was taken without knowing such ailment in advance.