As the phone has no way of knowing what your plan allowance is, it just shows how long you've been on calls. Keep in mind that not all calls are billable. My carrier doesn't count calls to customer service. So, if you had called customer service, it would show on the phone as usage but not on your bill as part of your allowance. Check to see if your carrier has an app in the App Store for tracking minutes. It will be much more accurate.