A method of operating an elevator system , the method comprising: receiving a first elevator call from a mobile device on a first floor, the first elevator call including a destination request to travel to a second floor; moving a first elevator car to the first floor in response to the first elevator call; moving the first elevator car (204-1) away from the first floor; detecting acceleration data of the mobile device; detecting elevator acceleration data of the first elevator car; comparing the acceleration data of the mobile device and the elevator acceleration data of the first elevator car; determining whether the mobile device is within the first elevator car based upon the comparison of the acceleration data of the mobile device and the elevator acceleration data of the first elevator car; determining that the mobile device is not within the first elevator car when the acceleration data of the mobile device is not about equal to the elevator acceleration data of the first elevator car; detecting elevator acceleration data of a second elevator car (204-2) when the second elevator car is moving away from the first floor; comparing the acceleration data of the mobile device and the elevator acceleration data of the second elevator car; determining that the mobile device is within the second elevator car when the acceleration data of the mobile device is about equal to the elevator acceleration data of the second elevator car; characterized in that the method further comprises: determining that the second elevator car is moving towards a destination floor that is a secure floor; determining that a person possessing the mobile device does not have access to the secure floor; and preventing the second elevator car from moving to the secure floor. receiving a first elevator call from a mobile device on a first floor, the first elevator call including a destination request to travel to a second floor; moving a first elevator car to the first floor in response to the first elevator call; moving the first elevator car (204-1) away from the first floor; detecting acceleration data of the mobile device; detecting elevator acceleration data of the first elevator car; comparing the acceleration data of the mobile device and the elevator acceleration data of the first elevator car; determining whether the mobile device is within the first elevator car based upon the comparison of the acceleration data of the mobile device and the elevator acceleration data of the first elevator car; determining that the mobile device is not within the first elevator car when the acceleration data of the mobile device is not about equal to the elevator acceleration data of the first elevator car; detecting elevator acceleration data of a second elevator car (204-2) when the second elevator car is moving away from the first floor; comparing the acceleration data of the mobile device and the elevator acceleration data of the second elevator car; determining that the mobile device is within the second elevator car when the acceleration data of the mobile device is about equal to the elevator acceleration data of the second elevator car; characterized in that the method further comprises: determining that the second elevator car is moving towards a destination floor that is a secure floor; determining that a person possessing the mobile device does not have access to the secure floor; and preventing the second elevator car from moving to the secure floor. determining that the second elevator car is moving towards a destination floor that is a secure floor; determining that a person possessing the mobile device does not have access to the secure floor; and preventing the second elevator car from moving to the secure floor. <EOS>