I am new to smartphones and thought that this might be good for others who are new and don't have the unlimited data plan grandfathered in to know. This was posted in reply to another question I had had about Pandora so the credit goes to poster MeVirtually. By default the wi-fi setting is set to go to sleep (and use cellular data instead) when the screen is off, which will most likely happen while you are streaming music as well as other things. To change it so the wi-fi never turns off, to into the phone's menu -> wireless and network -> wi-fi settings -> tap the menu button and select advanced which has an option for wi-fi sleep policy that had been defaulted to sleep "when screen turns off". There you have the option to change it to "never" or "never when plugged in".