A portable electronic device displays, on a touch screen display, a user interface for a phone application during a phone call. In response to detecting activation of a menu icon or menu button, the UI for the phone application is replaced with a menu of application icons, while maintaining the phone call. In response to detecting a finger gesture on a non-telephone service application icon, displaying a user interface for the non-telephone service application while continuing to maintain the phone call, the UI for the non-telephone service application including a switch application icon that is not displayed in the UI when there is no ongoing phone call. In response to detecting a finger gesture on the switch application icon, replacing display of the UI for the non-telephone service application with a respective UI for the phone application while continuing to maintain the phone call.