Or maybe you don't want other person (nearest one) to see your chat history, you need to delete the chat history soon. Not enough only using End Chat, because with end chat only make it disappear from displaying and still be in memory (storage)
Here is the way to clear your BBM history chat in Blackberry with V5 OS. Others version are not too different.
• Open The Blackberry messenger
• Choose contact that you want to delete it's history
• Click on Menu (Blackberry logo )
• Click on View Chat History, the chats will appear
• Click on Menu again, then choose Delete History ( there are two choices Delete Contact's History or Delete Complete history, Contact's history is for individual contact that we choose at the step 1, Complete history will delete all contact history chats).
After deleting, to make sure the Chats History already deleted, go to the View chat history menu again. repeat the steps if the chats not yet deleted.
See also :
• How to open and unhide the hidden file/picture in Blackberry
• How to Hide Photo or Picture in Blackberry device
• 'Ghost' Picture Using your Blackberry Camera
• How To know The Version of Blackberry OS