I can guide you to another discussion on the same topic. Meanwhile, I'd like to know why do you want to cancel the policy,is that because you feel that may not need the protection in the future. If so, then I'd request you to reconsider all the aspects before taking this decision. It may happen in the future that you lose our insurability at the time you need the coverage the most.
All insurers have certain procedure of policy cancellation. Some may allow cancellation only before the renewal of the policy. Hence, you're required to know their exact procedure.
You can get the idea from the policy document where they might have elaborated the process or else is required to contact the insurer's office to know the detailed method.