If you want to change your Viber number, simply deactivate your Viber account and reactivate with your new number (this restarts the setup process). To do so, go to "settings" in the Viber app.

Deactivation:

1. Open Viber

2. Tap on the three dots ('more') icon in your device's menu.

3. Tap on 'settings'

4. Tap on 'Deactivate Viber'

5. Tap on 'ok' when the warning notification pops up.

6. You will receive a verification that your deactivation was successful.

Now reactivate your Viber account using your new phone number. To do so run the setup again. Enter the new number that you'd like to use. This will erase your previous Viber number and replace it with the new one.

http://facebook.com/viber
http://twitter.com/viber