How can I place a cancellation for the WhatsApp Business API?
You can cancel the subscription of a number by following the steps which are explained here:
When you tick “Cancel subscription”, the termination date will be calculated and the WhatsApp Business API Client will be queued for deletion.
After deletion, you will no longer be able to send or receive messages. The phone number will remain in the 360dialogHub with an inactive status should you want to re-activate it in future. The subscription is terminated at the end of the month.
Meta will then require you to have 30-days free from sending paid messages before they’ll allow the number to be disconnected. Meaning, the number can only be used again with the Business or consumer app once it has been successfully disconnected from the API.