Hey! There are a lot of third-party providers that handle the infrastructure to avoid spam on iMessage. We use one and haven't had a problem with them.
As for WhatsApp, the business version has no problem with that either. It's just a cloud storage for user messages, and you can access it via API. There are plenty of bots providing third-party services for customer support for example
As for WhatsApp, the business version has no problem with that either. It's just a cloud storage for user messages, and you can access it via API. There are plenty of bots providing third-party services for customer support for example