I would like to know if there is an API or a way so we can know if a phone number is enabled/using Whatsapp.
On other hand, based on my test I fond that this endpoint api/v2/conversations/messages/agentless returns 202 whether the number ("toAddress") is using Whatsapp or not.
Hi Ali --
I can help with your question. We don't currently have a way to check to see if a specific phone number has a WhatsApp account, but we do have this on our longer term roadmap as a function we want to add.
Our WhatsApp Notification API (currently in beta but planned to be released in GA soon) does do a check behind the scenes before sending a message, if that number is not a WhatsApp number then an error will return indicating that the number is not on WhatsApp - however this is not the intended use of that API as you are actually attempting to send a WA message to the user when using that API so it shouldn't be used for the purpose of understanding if a phone number is on WhatsApp.
I also need to mention that it's required to have an Opt-In from a customer indicating that they consent to allowing messages from the brand across WhatsApp, so you should only message them with that consent.
One way we see this accomplished is through inbound voice or SMS flows, asking the customer if they want to use the WhatsApp channel, if they agree then they are Opting In and also indicating that they have a WhatsApp account.