You may want to use an existing number that you are already using on your phone with WhatsApp or WhatsApp Business, however there are a few caveats to this approach:
Please note: If you don't mind losing your chat history and would like to utilise a number that your customers are already familiar with, adopt this option. If you decide to go with this method, be sure to export your crucial chat history or create a backup on Google Drive or iCloud before cancelling your WhatsApp account. Be aware that this decision cannot be reversed, and your conversation history cannot be obtained.
If you already use WhatsApp Business, you might be wondering, "Why do I need to remove my WhatsApp account from phone?”
Although WhatsApp Business and WhatsApp API may appear to be the same from the outside, they are actually two distinct products. On the one hand, there is the standalone WhatsApp Business app, which you can use to manage your business account. However, it may be fairly constrained in terms of business functionality, as you cannot utilise the same number on two distinct WhatsApp apps or implement automations.
On the other hand we have WhatsApp Business API, which is the official set of APIs offered by WhatsApp to bigger businesses, which you can use to integrate WhatsApp into an existing app or system (like noApp).
Because a phone number may only be linked to one WhatsApp product at a time (the WhatsApp App, WhatsApp Business App, or WhatsApp API), you must delete your WhatsApp account before attempting to switch to WhatsApp API.