Short answer: An Alternate Number is a backup destination for calls to a user or extension. If the primary number can’t be reached, the call automatically fails over to the secondary number.

When it triggers

Calls fail over to the alternate number when any of these occur:

• The primary number is unreachable (power, network, carrier issue).
• The user is offline, logged out, or in Do Not Disturb.
• The call rings out with no answer within your timeout (for example, 20 seconds).
• The primary device is busy and your policy is “forward on busy.”

Result: The caller is connected to the alternate number without redialing.

Prerequisites

• You have Admin or Number Management permissions.
• You know the user’s extension (e.g., 101) and a valid alternate number (E.164, e.g., +1 415 555 0199).
• Decide your failover rule: unreachable only, or unreachable and no-answer.

Set it up (UI)

1. Go to Admin Portal → Users → select the user.
   Direct link: https://app.yourcompany.com/admin/users
2. Open Numbers & Routing → Alternate Number.
3. Toggle Enable Alternate Number.
4. Enter the secondary number (e.g., +14155550199).
5. Choose When to forward:
• Unreachable only, or
• Unreachable and no answer after [15–60] seconds.
6. Click Save. Changes apply within one minute.