Before you can setup a WhatsApp Business number, you will need to have your Facebook Business verified.
Facebook requires some documents that match the business entity with the registered bank account and/or alignment with documentation
About Facebook Business Verification:
Here are the steps regarding Facebook Verification:
Official Documents required for verification:
(Please note that Business Verification is not related to verified badge for your Facebook page. https://www.facebook.com/help/1288173394636262)