I need to update my phone number!

Dear @Raven,

Thank you for posting your question in the Microsoft Q&A forum.

Based on your description, you changed your phone number, and you cannot access your account because old number is no longer in service.

For better understanding and support you effectively, could you please verify that

• Do you mean that you need to update your new phone number in your MFA authentication settings so you can access your account?
• Which type of account are you using? (Personal account or business account?
• Are you a user or global admin of your organization?

In the meantime, if I am correct and you're using business account and you're an user. So you cannot change your MFA phone number yourself if you cannot sign in. I recommend you contact to your IT/Admin of your organization so they can help you update new number phone in your MFA. As forum moderator, I do not have administrative access to change these settings. Only your IT team has the ability to update new phone number, adjust or reset your MFA configuration. You can also refer to this Microsoft support article for more information: Manage authentication methods - Microsoft Entra ID | Microsoft Learn

And if you're unsure who your Global Admin is, this guide may help How do I find my Microsoft 365 admin? - Microsoft Support   .

In case you're only admin and you are completely locked out from the tenant. You might need to contact Microsoft Support team via phone service number: Customer service phone numbers - Microsoft Support. The agent will be able to create a ticket for you under the affected tenant and then transfer this ticket to Data Protection team who could help you to regain access.   

I hope information above helpful, if I misunderstand your point, please correct me so I can support you more effective.

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