iPhone 4 as WiFi

I have ab iPhone 4 that I have been using successfully as a wifi device. I still have the WiFi connection.

I notice that in the upper right hand corner that it says "No Service". I have been listening to Jazz 24, an online jazz radio station, using an app from the app store. Recently it stopped working, so I deleted the app and downloaded it again. Now it doesn't work. I get the message "This app will not function without network connectivity. Please restart app when signal is present." I DO have wifi working, just no carrier.