I have a 4500, too. I don't believe it has any type of light indicator as to whether there is service or not. The only thing it has is an alert (go under "Settings" then "Sounds" then "Alerts" then "Service Change"). I don't have my service change alert on, but it should beep (or something) when the phone changes service areas, like if you go from having service to having none. Hope this helps!