How to change admin roles without having access to the only admin account

You will need to contact microsoft and prove that you are the owners of the M365 tenant, they should be able to help. It would probably be easier if you can contact the person who has left and ask them for the logon credentials that they used.

Hi @Juan Rios Carranza
Thank you for posting your question in the Microsoft Q&A forum. 

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Regarding your situation, if the only Global Administrator has left the organization and no other Global Admins remain, this is considered a tenant lockout scenario. In such cases, the recommended action is to contact Microsoft Support directly via phone. You can find the appropriate contact number here: 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 DataProtection team who could help you to regain access. 

To proceed, you’ll need to provide documentation to prove your organization’s ownership of the tenant. This typically includes: 

-Domain ownership (DNS management access). 

-Billing/subscription details (payment methods, account history). 

-Tenant ID of the locked organization. 

-Business registration documents. 

-Authorized signatory documentation. 

Please be aware that the Data Protection team often experiences high volumes, so it may take 3–10 business days to receive a response. While this may not be the most immediate solution, it is currently the only supported method to recover access in such scenarios. 

If possible, reaching out to the former Global Administrator to retrieve credentials or have them assign another Global Admin remains the fastest resolution. 

For future prevention, we strongly recommend designating at least two Global Administrators to avoid similar issues. 

When a call is made to support, the first step is to provide an automated voice response from AI. Be careful, you won't be able to speak to a support representative if you don't respond appropriately here.  

Here's an example of a response that actually led to a support representative. Please refer to it: 

Q. Can you tell me if you are calling as a home user who uses a product or service at home or a business user who uses it in your business to provide the best assistance? 

A. I am a business user. 

Q. Thank you. Can you give me the details of your inquiry? 

A. Login technical support. 

Q. First of all, can you tell me which products you are inquiring about today? 

A. Microsoft 365 business Standard。 

Q. Please wait a moment, I understand Microsoft 365. Are you calling about a new case or an existing one? 

A. New. 

Q. To receive phone support, your phone number must be associated with your Microsoft 365 admin profile. To do this, go to aka.ms/m365profile. Again, it aka.ms/m365profile. This can take 48 hours. In the meantime, you can go to aka.ms/m365profile and file a case online. If you prefer, you can also text the link to the phone number you are calling. What do you think? 

A. The phone number is already linked to the link. 

Q. Can you tell me about the products in your inquiry? 

A. Microsoft 365 Business Standard. 

Q. Are you a Global Administrator? 

A. That's right. 

Q. I'm sorry. I didn't understand. Are you a global administrator for your domain? 

A. Yes, I am a global administrator for the domain. 

Q. If you have any inquiries, you can contact a Microsoft representative. Are you sure? 

A. Yes. Please. 

Q. Yes, I understand. One moment. 

I hope this information is helpful. 

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