With the Change number function in the WhatsApp Business app, you can change the phone number that is currently linked to your WhatsApp Business account. When the phone number is changed in WhatsApp, the following happens:
The account information (including profile picture, name, profile info, all chats and settings) are transferred from the old phone number to the new number.
The account that was linked to the old number is deleted so that contacts no longer see it in their list of WhatsApp contacts.
Instructions
In your WhatsApp Business app, tap on More options > Settings > Account > Change phone number > Next
Enter your old number in the first box and your second number in the second space (both including the country code). Then click Next at the bottom of the screen.
If you like, select Do not notify contacts on the next screen. Please note that group chats will still be notified when you change your number, even if you choose not to inform individual contacts. Then click Done.