TATA AIG General Insurance - TATA AIG insurace claim issue

This is to bring to your notice that I have faced problem with my *-wheeler insurance company regarding accidental claims. The whole scenario is mentioned below.
I am using a Hyundai Grand i** car (Reg. no.- DL*CQ****) which has been
insured by TATA AIG. The policy is a zero depriciation policy. In month of March back I have installed CNG Kit in my car and informed the insurance company regarding the same (Pic attached for reference). I have asked the insurance company to upgrade the policy and tell me the requisite amount required for the endorsement. I have called the insurance company many-a-times and even used their online chat system, but the insurance company didn't took action on it. Nor the company's online portal shows any option of online endorsements.
I asked the company to send the any person to my home/office address for inspection and required paperwork, but nothing happened.
During the month of June my car met an accident causing major damage to the body structure. The insurance company asked me to pay **% of the total settlement amount because of non-declaration of the CNG to company. The paper they send for signing the form wasn't printed on official letterhead, nor carrying company's stamp (pertaining to customer's forced acceptance by claims department's own will). While I have informed them on mail, calls and chats. They didn't hear anything and asked me to pay the amount (Rs **** approx.). Also this case took ** days to settle because of the delay by the insurance company.
I have tried to explain that the accident occured was not because of CNG but by external means. This all has costed me a huge loss of money and time and a lot of inconvenience.
After the settlement when I went to office for endorsements they said they will send the inspection person to my home/office address for the same.
I want consumer court to intervene in between and take necessary action against the company. Because of the negligence of company I have to pay a huge amount and suffered lot of inconvenience and mental stress.

Since the policy was taken online, the endorsements or modifications should be done online too or should be facilitated as per customer's convenience.

All the requisite documents are attached herewith for your reference. Kindly review.
Car Reg. no- DL*CQ****
Policy No- ********** (Tata AIG)