WhatsApp Business API restrictions
One of the things to keep in mind is the 24-hour limitation while using the WhatsApp Business API. This means that as soon as a customer sends a WhatsApp message to the company, the company is given 24 hours to respond to this message. This way a so-called 24-hour session is started. Within these 24 hours, a normal conversation can be conducted in WhatsApp in which both parties can respond. If you are not able to respond in 24 hours two alternatives enable you to continue the conversation. You can either send an SMS or make use of WhatsApp Templates. Starting a conversation initially is only possible with the use of WhatsApp templates on WhatsApp Business API.

Downgrade restraint
Once a phone number is registered on the WhatsApp Business API, it cannot be used for WhatsApp Business or the WhatsApp consumer app. A phone number can be upgraded to the WhatsApp Business API, but never downgraded. More information on the WhatsApp and Facebook policy around this matter can be found in the Facebook developers guide.

Group chat
Currently, WhatsApp group chat is not supported within the WhatsApp business API.

Calling through WhatsApp
Currently, WhatsApp doesn't support calling through their WhatsApp Business API.

Application process
A WhatsApp application takes time. There are several steps necessary to take by the organisation, Casengo, and our business partner. These steps your organisation will need to take:

Start the application via Casengo
Accept Facebook Invite and start verification for Facebook Business account*
Sign the terms from WhatsApp via HelloSign (we will send it to you)
Activate your phone number in Casengo
* To smoothly proceed with the application please be aware that you will need a verified Facebook Business account. Verifying your Facebook Business account is a process that is done by Facebook and we do not influence the estimated time of approval. Please take into account:

The Facebook Business ID cannot be changed during the application process, if you want to change the ID you will need to start a new application.
The registered number cannot be changed during the application process, if you want to change the number you will need to start a new application.
It is not possible to receive a refund when you cancel after the application process is started.
When all steps are taken accordingly our experience is that the application takes about 1-2 weeks (excluding Facebook Business verification time). Disclaimer: this may vary and depends on the reviewing speed of Whatsapp and Facebook.