Multichannel messaging is currently in its beta-testing phase, and is available as part of an early access program we're running for customers. If you're keen to give it a try and let us know how it goes, get in touch with us and we'll see about getting the feature added to your account.
To get you set up, first, we need to grab some details about your business. Google will use these details to verify your business and set up your new Google Business Messages account.