# Find Sms Auth Phone Number

### Description

This runbook searches for which user has a specific phone number registered with SMS Sign-In enabled in Microsoft Entra ID. Unlike regular phone MFA methods, SMS Sign-In numbers must be unique across the tenant. If a number is reserved for SMS Sign-In by one user, assigning it to another user will fail with a "phoneNumberNotUnique" error. Regular phone MFA methods do not enforce uniqueness. This runbook helps administrators identify which user holds a specific SMS Sign-In number for troubleshooting and remediation.

### Location

Organization → Security → Find SMS Auth Phone Number

**Full Runbook name**

rjgit-org\_security\_find-SMS-auth-phone-number

### Permissions

#### Application permissions

* **Type**: Microsoft Graph
  * AuditLog.Read.All
  * User.Read.All
  * UserAuthenticationMethod.Read.All

### Parameters

#### PhoneNumber

Phone number to search for in E.164 format (e.g., +492349876543). The number must start with a "+" followed by the country code and subscriber number.

| Property      | Value  |
| ------------- | ------ |
| Required      | true   |
| Default Value |        |
| Type          | String |

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