App Store
https://apps.apple.com/us/app/whatsapp-messenger/id310633997
Google Play Store
https://play.google.com/store/apps/details?id=com.whatsapp&hl=en_US
WhatsApp Secure Messaging and Calling
Many churches and individuals are using WhatsApp to share audio and video sermons, texting, and more. It can be used to share the gospel. I think many people in many different countries use WhatsApp because they can make free telephone calls to different countries and also send texts for free. You can call people and share the gospel. Many times, the audio and video quality is better than what you would expect.