First go to the ‘Chats’ page. You can do this by selecting the far left icon at the bottom of your Sylo home screen.
Next, tap on the name of the contact you’d like to delete the message history with. This will open your conversation with them.
Tap the ‘three dots’ icon in the top right-hand corner of the screen, now click on the ‘Delete Message History’ button and confirm your action.
Note: This will delete your message history for you, but not for the contact.