I PRESS A SONG AND ANOTHER ONE PLAYS ON IPHONE

I TRY TO PLAY A SONG, WHEN I PRESS IT IT PLAYS ANOTHER SONG!

That happened to me once, it turned out someone hacked it. I had to get the geek squad to fix it. The person deleted Marilyn Manson off my phone and added Pearl Jam. I did keep the Pearl Jam though. Before it was fixed I was listening to Lynyrd Skynyrd and they blasted the volume all the way.