The number is the part of an application people most often get wrong, because a number that works fine for calls may not be usable here.
A number can be used if
- You own it and can receive a code on it
- It is not active on WhatsApp or WhatsApp Business right now
- It can take an international SMS or voice call
- It stays reachable — the number must remain yours
A number cannot be used if
- It is already registered on the API with another provider and not released
- It is a short code
- It cannot receive verification from outside your country
- It belongs to someone else, including a personal number of a staff member