D4D Chat
After completing the first steps as described here, an overview will open up, which will display, among other things, the chat.
You also have the option to access the chat through the dropdown menu located at the top left in your D4D app. ➡️
click image to zoom
By entering your message into the input field (1) and clicking the send button (2) next to it, the message will be forwarded to the dispatcher.
All chat communication of the drivers who were logged in with the vehicle before you, is visible to you. And that will be the case for your communication as well.