Short answer: buy a new business SIM from a real mobile carrier and register that. This is not a decision worth agonising over, and the people who agonise over it are usually circling the one thing that actually matters – which number not to use.
The one thing that matters
A phone number can be on the WhatsApp Business Platform, or it can be in the WhatsApp app. Not both.
If the number is already using WhatsApp – personal or the WhatsApp Business app – you have to delete that account before you can register it on the API, and deleting it removes the chat history. Permanently. There is no export that restores it into the API and no support request that undoes it.
So the number printed on your website, the one customers have been messaging for two years, is the one number to leave alone. That is the whole trap. Everything else here is a detail.
What to buy
A standard mobile SIM from a normal carrier, in the country your business operates in, on a business account. Nothing clever.
Two things worth a moment’s thought while you are at it. Get a number that is easy to read and remember, because it will end up on your site, your invoices and your signature. And keep the handset – you need it to receive the verification code at registration, and again if you ever re-register.
That is the decision. It costs very little and it takes an afternoon.
What not to use
- VoIP and virtual numbers. Don’t. Verification is unreliable, the number is not really yours, and you will spend more time troubleshooting it than a SIM would have cost.
- Disposable or shared online numbers. Often already registered by someone else, and you have no control over who holds them next.
- Anyone’s personal number. It stops working as their personal WhatsApp the moment you register it, and it leaves when they do.
- A number you do not control. A client’s line, or anything on a contract you are not the holder of.
- Your live customer-facing WhatsApp line. See above. The history is the cost.
Keeping your existing number working
The common real-world situation: there is an existing WhatsApp Business app number full of live conversations, and you want the API without losing them.
Run the new number on the API and leave the old one alone. Point new traffic at the new number – website button, click-to-chat links, ads, email signature – and let the old one wind down as those conversations close.
Two places to check for a while, and nobody loses a conversation. Usually the better trade.
The name customers see is separate
Your display name is not your phone number and is reviewed on its own. It has to relate to your actual business, so use the name customers already associate with you rather than an internal project name. It sits at the top of every conversation.
In one line
Buy a proper business SIM, keep the handset, and don’t touch the number your customers already message.
Meta’s requirements for phone numbers and display names change from time to time. Check the current documentation before registering.