Clearing your thread history with a particular contact or group deletes all of your past conversations and call logs from a Light Phone. This is a permanent action that cannot be undone. Clearing the history does not block the contact from future communication, it only deletes the history itself by removing their name/number from your recents list. Clearing does not delete the contact itself from the phone.
How to clear your history with a contact/group:
There are a few ways to clear a thread.
From the main recents list, you can long press any conversation thread to jump to their contact details, where you can CLEAR the history with that contact or group.
You can also swipe from the left side of a name/number from the recents list, to bring up a shortcut for clearing the thread. Pressing (x) will ask you to confirm that you'd like clear the conversation.
If you have the thread with the contact or group, click the name/number of the contact at the top of the thread to open up the "Edit Contact" page where you can CLEAR the conversation.
How to clear all of your history:
You can clear all of the phone's history in the settings as well.
Settings > Account & Info > Storage:
There are a few options on this screen:
Clear Phone History: this clears all conversations on the phone. All contacts are still saved, just the history of calls/texts.
Clear MMS History: this saves the text/call history, but will delete any images/videos that were sent to your Light Phone.
Keep History Setting: this settings allow you to automate the clearing of threads automatically after 30 days if you'd prefer.