How should I implement opt-in for WhatsApp?
First, the customer can only give their consent via a ‘third party channel’, an opt-in form on one of the business’s existing communications channels, such as email, website, SMS, app, dedicated landing page, etc. Opt-ins should be active, meaning that the customer must actively show their consent by entering/editing a phone number or by checking a box.
Secondly, businesses must be clear on what customers are signing up to—and what type of information they will receive once they have consented.