My cars parked a 5 minute walk away otherwise I'd check, but from memory, 'Phone' is displayed on the radio when:
1) I turn the ignition on, presume this is the bluetooth pairing and its only displayed for a few seconds
2) I receive a call
3) I press the steering wheel controls to instigate a call. I think it comes up as soon as the controls are pressed, so it starts before before dialling has started.This is why I thought one of the buttons may be stuck down.