Stop audio files playing when I plug in USB

[DrWu]

My new car has a USB port which I really only use for charging my phone but whenever I plug it in, the phone takes over my sound system and just starts playing every audio file I have on the phone, one after another. It starts with the sample "Horizon..." song that Samsung includes on the phone and continues playing every single file - old voice mails (my home voice mail is emailed to me), voice recordings, etc. Looking at the phone there is no indication that anything is playing, its only showing up on the radio. Any way for me to stop this from happening?