Well, first of all, you can choose not to confirm your phone number with Google+ when Hangouts starts on your new phone for the first time in the first place. If you already have consented, then you can go to your Google Plus account settings. Then under Phone, go to Edit, then click the "edit" link next to the number you want to remove or edit. Google has updated the settings, making it possible to completely remove the number if you wish. If you simply want to keep Google from using it on caller ID but want to leave the number in your account, you can also do so by unchecking a checkbox that appears right below the given number.