A clear case of cheating by the insurance firm. As far as I know, any one with a valid driving license can drive any one's car and in case of accident, the owner can claim the insurance.
The reason I am quite sure about this as my car is bought on a company lease (wife's organization) and I did claim insurance as the incident occurred when I was driving the car.
Unlike in the US, where in we have to add the additional driver and buy insurance for the additional driver. In India, there isn't any such rule.
Fight it out and take to consumer court.
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