Oxy look no further, help is here! We'll get right to work to see what is causing the trouble with adding the appointments. Are you syncing your calendar with an email account? Have you recently made any changes to the device?
Follow us on Twitter @VZWSupport
I am sorry you're not able to use your calendar. To confirm, are you using the iPhone 4s or a different device? What error messages are you getting? Try doing a soft reset to see if this refreshes your device to allow you to access the calenda function and post back with more details.
Follow us on twitter @VZWSupport