Thank you for posting this in Microsoft Q&A.
As I understand you are unable to access Azure portal with your account. You had set up MFA for your account initially via Authenticator App. Now since you have changed the phone and installed new Authenticator App on your new phone, you have lost all the account from the App.
Due to this you are unable to satisfy MFA while logging in to Azure portal.
As you already mentioned you are the only admin in your tenant and your account is blocked currently from accessing Azure portal, you can reach out to our support team. You can look into below article to get support numbers depending on your country.
Except this method there is no other way to get your account logged in to portal, as this is something related to security of your tenant.
As per your above comments I see that you have also already reached out to customer service but couldn't get any help.
This time when you call them you cannot access your Azure tenant, and you want to talk to someone from data protection team.
They will help you in creating a new support ticket. Give them the tenant ID which is locked out in your description. Tell them that no admin account has access anymore and your partners also have no access anymore.
Once your ticket is created with support team you will have to work with our data protection team. You will have to first prove your identity against your tenant for security purpose. Post that this team will help you with help you in getting access to your tenant or unlock your account depending on your scenario.
Also, for the future, you can create an emergency access account (break glass) in Azure AD. This account will help prevent being accidentally locked out of your Azure Active Directory (Azure AD) organization because you can't sign in for any reason.
https://docs.microsoft.com/en-us/azure/active-directory/roles/security-emergency-access
Let us know if you have any further questions on this.
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