If the amount of hours driven exceeds the bought hours from the policy then first off you should think if this is a one time disparity or a reoccurring event. If you've made sure that you need to change the hours driven in the policy, you should cancel the active insurance and start a new one with the correct hours on the correct date (from the date of the old insurance policy end). You can change the amount of hours at app.cachet.me/policy/modify.