The iPhone operating system does not allow for “backgrounding” between phone or text messaging on the one hand, and an application such as NPR News on the other. Thus, initiating or receiving either a call will force you out of the application temporarily. Under most conditions, you will be returned to the app once you have concluded calling or texting; however, you will have to restart any audio that you might have been playing. Receiving a text message will not disrupt the audio in NPR News, but if you click Reply or Slide to View, the NPR News app will be quit and you will have to restart the app to return to NPR News.
If you want to listen to a long program and do not want to be interrupted by phone calls, you can only do this in a Wi-Fi area by turning on Airplane mode, turning on WiFi and connect to the WiFi network.