With the "Change number" function in the WhatsApp (Business) app, you can change the phone number that is currently linked to your WhatsApp 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.
This is how it works
Open your WhatsApp (Business) app
Tap on More options > Settings > Account > Change number > Next
Enter your old number in the first box and your second number in the second space (both including the country code)
Tap Next
Now select Do not notify contacts
Your group chats will be notified when you change your number, regardless of whether you notify your contacts.
Tap Done and that's it 👏