Multiple Buttons To Change UI Text

OK I'm having a little success with this script but it needs help. Basically I need to toggle the UI text message with numerous buttons. As I say I'm having a little success with this one but it does not turn off the message to a default message.

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 public class MessageCentreManager : MonoBehaviour {
 
     //UI Text Reference
     public Text MessageCentreText;
     
     //Button States
     bool button01State = false; //Scanner
     bool button02State = false; //Auto Phone
     bool button03State = false; //Temperature
     
     void Update () 
     {
         if (button01State == true){
             MessageCentreText.text = "SCANNING";
         }
 
         else if (button02State == true){
             MessageCentreText.text = "AUTO PHONE";
         }
 
         else if (button03State == true){
             MessageCentreText.text = "TEMPERATURE";
         }
     }
     
     
     //Scanner Button For Message
     public void GoScannerMessage()
     {
         button01State = !button01State;
     }
 
     //Car Phone Button For Message
     public void GoAutoPhoneMessage()
     {
         button02State = !button02State;
     }
 
     //Temperature Button For Message
     public void GoTemperatureMessage()
     {
         button03State = !button03State;
     }
 }