Update a phone number

You need the "Manage Group Phone Numbers" permission to update a group number. You can only update your own personal numbers. You can: - Change a `label` of your number. - Set up call forwarding via `forward_to` and `forward_to_enabled`. - Set up a voicemail greeting by including a URL of an mp3 recording in `voicemail_greeting_url`. We require the URL to be secure (i.e. starting with https://). - Modify which team members are part of a group number via `participants`. This should be a list of user IDs. - Modify which external phone numbers are part of a group number via `phone_numbers`. This should be a list of phone numbers in E.164 international format, e.g. "+16503334444".