Hopefully I can help here.
Are you the only Global Admin on the tenant? If not, you can get them to disable it for you.
As part of the MFA setup, you should have been able to set up backup authentication methods on the account - e.g. additional email or text message (mobile number).
If none of those have been set, you'll need to contact Microsoft support. They will be able to verify who you are by billing information and remove MFA for you. If you are going through a Microsoft CSP (Cloud Service Providers), they should be able to help you with this too.
Contact numbers for Microsoft Support are:
United States, call 1 800 865 9408.
Australia, call 1 800 197 503.
Canada, call 1 800 865 9408.
United Kingdom, call 0800 032 6417.