There are a few ways you and your clients can chat using Travefy and Trip Plans.
Advisor Option 1: Trip Builder
Inside the trip builder, you're able to access the discussion panel here, on the right-hand side of your library.
Advisor Option 2: Before you Click "Edit"
Click on the correct itinerary and then click on the Chat tab at the top.
Advisor + Client Option: Web Link - Itinerary
If you're viewing an itinerary on the web, there will be a chat icon off to the right of your screen.
App Options:
Travefy Pro (for the advisor) and Trip Plans (for the traveler). Select the itinerary in the app and you will see the chat option in the top right corner
What about turning the messaging feature off?
To do that, you can follow the instructions here.