If you check your policy with Travelers you should find that it is a requirement for you to notify them in writing that you wish to cancel your policy. Insurance companies do this because they are required to give you a grace period (normally 30 days) in case you forget a payment, are late on a payment or your payment goes astray. Basically, if you do not notify them, they are liable for any claims in that grace period and you are liable for the insurance premium payment for that grace period. Your sending them written notification relieves them of any responsibility from the time you notify them and your charges should be prorated as such.