Why can’t I click confirm if I choose the Free trial plan for WhatsApp?

Why can’t I click confirm if I choose the Free trial plan for WhatsApp?

WhatsApp channels are not included in the Free Trial plan as WhatsApp requires to have a dedicated server for each WhatsApp number. We will start and charge the monthly subscription (i.e. US$99) once you have completed WABA onboarding and deployed the WhatsApp server. 

Since the US$10 credit included in the Free Trial plan is only for users using the Facebook Messenger and Web Chat Channel, the On-Demand Plan will be automatically selected for you if you have added a WhatsApp Pending Channel.