A:Answer Hi. This is Junry from TracFone Wireless. Regarding your concern, AUX can be used for MP3 player.Earphone. If you plug your speakers, microphone, or headphones into your main device, with the possible exception of some types of USB setups, you're usually connecting through what's called an aux port. For further assistance, please chat with us via this link https://www.tracfone.com/support/contactus. For your convenience, our representatives are available Monday-Sunday from 8:00 AM to 11:45 PM EST. You can also use our self-service menu by simply texting the word HELP to 611611.