How to delete old messages.

Does anyone know how to delete old messages? Initially I had to do them one at a time. Now i can delete the content but the photo and name on the left side ..... won't delete/dissappear. Anyone out there can help me? Please

I usually have to refresh the page and then they picture and name disappear. 

whoops, I'll fix that tomorrow that the conversations list is updated after you deleted a conversation.