Press and hold the POWER button for about 20 seconds. This will force the unit to a soft reset. Then follow Polaris OBark's suggestion.

"No, Garmin, I don't want to give you tel numbers/info of other people." Oh, I wouldn't worry too much about that. After all, anytime you use a GPS unit on your ride, your location information is transmitted to the mother ship of the aliens from Flattirera, who then decide if they want to send down their death ray beam to your wheel and free all the trapped air inside.