Regarding the admin MFA issue only phone support can help and ask them to escalate your issue to the data protection team.
Here are some tips and an example of a prompt to help you navigate the IVR more effectively:
In some countries, it is an automated conversation like: First, when you call the hotline, it will be asked as follows:
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 confirmation: 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
You also need to provide your subscription purchased information such as company name, billing information, phone number etc. See: https://learn.microsoft.com/en-us/microsoft-365/admin/get-help-support?view=o365-worldwide#phone-support