on iphone 6plus, how do I turn off pandora radio

Hey romangerj,
If Pandora is playing in the background and you are done with listening to that app, you can force close the app. To do that, double click the Home button to bring up the preview of other apps that have been opened. You can than swipe up on Pandora and that will close it completely out. Also another alternative is bring up Control Center and use the play controls to pause the music. For more information, take a look at the links below.
Force an app to close in iOS
https://support.apple.com/en-us/HT201330
Use Control Center on your iPhone, iPad, and iPod touch​
https://support.apple.com/en-us/HT202769
Have a great day