Add your own business phone number

First, You need to go to your apps in Facebook developer, and add your own phone number,

Click “Get started” and then click “Add phone number” in step 5 as per the screenshot below:

You need to provide the information to create your WhatsApp business profile

And then you can add a phone number for WhatsApp, you need to verify your phone number by receiving a text message or phone call.

After you verify your phone number, you will just need to wait for Facebook to approve this number, and then you can sync the number back to Cloud API channels.

After you submit the information, you will receive certification & display name confirmation from Facebook.

As per the screenshot below:

And you will also receive emails from Facebook about the new number you just applied for.

You need to closely monitor the status in your WhatsApp business manager, and make sure it’s connected, not pending.

You will be able to switch when the status is Connected, not pending.

Please note:

You can not use your existing WhatsApp number on the WhatsApp Cloud API.

You will either have to delete your existing WhatsApp account and then you can use the same number in the WhatsApp Cloud API or you need to get a totally separate number for the WhatsApp Cloud API account.

We recommend you get a new number for the WhatsApp Cloud API.

You can still use the number for everyday purposes, such as calling and receiving messages after registering it on the WhatsApp Business Platform.
Once you use a phone for WhatsApp Automation you can no longer use that number on the WhatsApp Business App or WhatsApp personal app.