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Have the same mobile number for authentication method

Joseph Smith 20 Reputation points
2025-01-10T10:23:38.2966667+00:00

I onboard our users, by creating there accounts in Azure and logging on to the computer as them and preparing everything. I set my phone up for authentication so I can complete the process. Once laptop is set up, before giving to user, I change the authentication number to their own mobile. Lately have been unable to perform, as I am informed that the number is in use. Is there a way to allow me to temporarily assign my number to complete the registration and change on completion?

Microsoft Security | Microsoft Entra | Microsoft Entra ID

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  1. Anonymous
    2025-01-16T14:41:19.1966667+00:00

    Hello @Joseph Smith,

    We understand that as a part of onboarding your users, you are creating user accounts and for completing the authentication process you are temporarily assigning your mobile number to the users which you are changing to their own number later. In this process, you have observed that you are not allowed to add the number as you are informed that the number is already in use.

    As a part of our troubleshooting, we have tried to follow the steps below.

    Enabled the authentication method policy and added targeted all the users in SMS-based authentication method as shown below.

    User's image

    We were able to add the same mobile number to the two test users here.

    Later, we have tried to configure SMS-based authentication as a first factor by checking in the below box beside user sign in which will allow users to sign in with this method.

    User's image

    Once that option is selected, we were no longer able to add the same mobile number to the test users. We have encountered a similar issue as yours stating that number is already in use.

    If the user sign in is enabled, it will no longer allow us to add the same number to different users as it will be used to sign in. Leaving this unchecked makes SMS-based authentication available for multifactor authentication and Self-Service Password Reset only.

    Hope this helps. Do let us know if you any further queries.

    Best Regards

    Janaki Kota

    If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.

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