The easiest thing to do is from Admin Panel got to Settings>Language Settings and in the "Look For:" box put in this:
_chat_page_caption and put a check mark in the Apply. Edit the string that it pulls up and type in whatever you want your Chat page to say. (This will change the name in the browser bar at the very top)
You can also repeat the same steps for _chat_box_caption and this will change the name of the caption displayed at the top of the Chat box.