Sole Global Admin locked out of Microsoft 365 after phone change (MFA)

Hi @호준 윤

As you are the only Global Administrator, this issue cannot be resolved through the community forum. I understand that you have already contacted Microsoft Support but were disconnected by the automated system. Please try calling again and follow the IVR steps below to reach the Microsoft Data Protection team, as only they can verify your identity, reset your MFA registration, and help you regain access to the administrator account. 

Please note that I am just a fellow user contributing to this community forum and community members do not have access to your tenant or the ability to escalate the case to the Microsoft Data Protection Team on your behalf.   

You can find the appropriate customer service phone numbers at this link: Customer service phone numbers.  

(Choose Work account scroll down to Technical support phone numbers and find the Phone number of your country)  

Please remember to provide them with your account details and explain the situation. Be ready to provide:       

• The company name used during subscription      
• Billing email address (even if it’s a personal Microsoft account)      
• Payment method details (last 4 digits of the card, billing address)      
• Any subscription ID or invoice numbers from billing email      

When you call the support number, you may hear an introduction of about 30 seconds such as "you can visit the link...". You can ignore this introduction and wait until you are presented with the options. Then press "1" as a business email user, and again "1" for technical help.  

To make the process smoother, here’s an example of how to respond when speaking to the automated system (IVR):       

IVR: What kind of problem are you concerned about?       

You:  Authenticator.      

IVR: What kind of product do you use?       

You: Office 365 for business.       

IVR: education or company account?       

You: For companies       

IVR: Are you an administrator?       

You: Yes.       

IVR: Do you have the other administrator in your organization?       

You: No.       

IVR: Do you need a... Service request?       

You: Yes       

These prompts help direct your call to the right support team more quickly, especially when dealing with account lockouts and authentication issues.  

If you are still unable to reach a Microsoft support agent, you may consider the following workaround: create a new Microsoft 365 tenant by signing up for a trial subscription through Compare All Microsoft 365 Plans. Follow the guided setup to create a new Microsoft account and tenant. 

Please note that free-trial availability may vary by region. After changing the locale to Korea, I could only find the option to start a new trial for the Microsoft 365 E3 Enterprise subscription, as shown in the screenshot. Please verify that this trial is suitable for your needs before proceeding.

Please note that this new tenant is only a temporary trial environment. It will not be connected to your original tenant and will not give you access to its users, data, subscriptions, or settings. You will only use the trial tenant to contact Microsoft Support and submit a ticket on behalf of the tenant you cannot access. 

After setting up the new tenant, sign in to the Microsoft 365 Admin Center. Follow the instructions in Get support in the Microsoft 365 Admin Center to submit a support request.  

In your request, ask to speak with the Data Protection team regarding your previous tenant and provide the following information:  

• The administrator email address associated with the locked tenant  
• The domain name of the locked tenant  
• Any error messages you are receiving  
• A description of the authentication or sign-in issue  
• Confirmation that you are an administrator of the locked tenant  

Before submitting the request, make sure Support Assistant is turned off. Some customers have reported that the Contact Support option may not appear while Support Assistant is enabled.  

As shown in the screenshot, switch Support Assistant to Off, and then enter a description of the issue. The Contact Support button should then appear, allowing you to submit the request.  

Important information  

• The new trial tenant will not provide access to any data, users, settings, or services from the original locked tenant. It is intended only as a temporary way to contact Microsoft Support.  
• Once access to the original tenant has been restored, remember to cancel the trial subscription to avoid unintended charges. In the Microsoft 365 Admin Center, go to Billing > Your products, select the trial subscription, and follow the available cancellation instructions. Cancel your subscription in the Microsoft 365 admin center 

I hope this information is helpful. Please understand that fellow forum users can provide only general guidance and troubleshooting suggestions. I do not have access to Microsoft’s internal systems, account recovery tools, or identity-verification processes, nor do I have the authority to reset authentication methods or restore administrator access. Any further assistance with account recovery must come directly from the appropriate Microsoft Support team