Apologies for stepping in before ED does, but this has come up before - lots of smartphones use a newer type of 3.5mm jack - if you look at yours*, you'll see it has 4 connection points on it. The Pandora uses the 'classic' original 3.5mm stereo headphone jack, this has 3 connection points. Your earphones will not be making the right connection, you can get an adapter to use them on ordinary 3.5mm sockets, otherwise you need to use headphones designed for audio equipment rather than modern smartphones.
* I know these (in the linked image) aren't Samsung ones, but they have the Samsung compatible plug.
Well ED doesn't need to address this, first off are they true headphones or are they a headset (have a microphone)?, If they do have a microphone then it's a problem with how the headset is wired..
So a bit of history, the Pandora was designed before the iPhone came out.. at the time there was an international standard of how a headset should be wired and it's what the Pandora, Nokia and every other company used.. However Apple comes out with the iPhone and they make up their own standard, flash forward a few years every phone company is now using apple's standard vs what was the international standard at the time.
A little trick I do with my headset at home is push down the microphone mute button on the headset and the sound issues should clear up..
Apple's Vs Nokia(international standard):
How the grounds are different between the apple standard and the pandora causes the audio not to be grounded properly, hitting the mute button on the headset will cause the audio to become properly grounded and the sound will clear up.. Currently I just use regular headphones.. If I must use my phone headset I use a twist-tie to keep the microphone mute button held down.