Ons Messages is the newest app within Nedap's Ons Suite. The app is still in pilot, so if your organization participates, you can use the app. Isn't that the case? Then ask if your organization can participate, or use Nedap Ons with which you can already send and receive messages, and more: https://play.google.com/store/apps/details?id=com.nedap.healthcare.milo