A system and method for determining the orientation of a mobile device for displaying a graphical user interface and for activating an audio user interface in response to an incoming call or outgoing call. For the graphical user interface, depending on the detected orientation of the mobile device, the graphical user interface can be displayed in a first vertical orientation, a second vertical orientation, a first horizontal orientation, and a second horizontal orientation. For the audio user interface, depending on the detected orientation of the mobile device, a speaker and a microphone can be activated based on the detected vertical orientation so that the activated speaker is near the top of the mobile device and the activated microphone is near the bottom of mobile device.