Lost Access to Authenticator and Old Phone Number

If you have lost access to your Microsoft account due to not having the authenticator app or your old phone number, you will need to follow specific steps to regain access. Since you are likely the only administrator on your account, here are some options you can consider:

1. Contact Microsoft Data Protection Support: You should reach out to Microsoft support directly. When you call, explain that you are locked out of your account and are the only admin. They will guide you through the process of verifying your identity and regaining access.
2. Use a Temporary Account: If you cannot reach a live agent, consider creating a new trial tenant. This will allow you to access the admin console of the new tenant and submit a support ticket requesting assistance from the Data Protection team on behalf of your original account.

Make sure to provide as much information as possible about your locked account when you contact support, including your administrator email address and any error messages you are receiving.

References:

• How Do I Regain Access to My Account After Losing Access to Microsoft Authenticator? (Urgent Request). - Microsoft Q&A
• I have a Micrsoft business account and I am the admin and the only user registered under this account. I can't log in because i have replaced my phone and the authenticator doesn't work. - Microsoft Q&A