What do I do if I already have Business WhatsApp set up with my personal mobile number?

If you’ve already set up Business WhatsApp setup with a different number, and want to change the number to your Air Landline number, you’d essentially need to do a number change in Business WhatsApp.

Here’s WhatsApp’s guide on changing your number: https://faq.whatsapp.com/498754122134583/

Here’s WhatsApps info about changing phone numbers: https://faq.whatsapp.com/1166321223998129/