Siri, Apple's trustworthy and dependent assistant will now make WhatsApp calls for you. Up until now, Siri was assisting only those apps which made sense when the user said something. For instance, making calls from the user's contact-list, paying bills, making notes etc.
WhatsApp has recently enhanced its call offerings with voice message service. Maybe other enhancements will follow soon.
Other than making calls, the Siri app will be able to send messages for you, or read the ones you receive out loud.