Free look period: If the policy holder doesn't want to continue with the policy, he can cancel it by giving the reason of cancellation of policy. (policybazaar.com)
But if you miss more than half of the total length of your trip because your travel is delayed, this situation may be considered a trip cancellation for insurance purposes. (allianztravelinsurance.com)
Some providers may charge a small administration fee for cancellation of policy, but it should not cost more than a few dollars. (travelinsurancereview.net)