Prank audios for you to play down the fone on your victim.
(This works with nokias the best!") simply save them to your fone, then call the victim up, put it on loadspeaker, then get into you menu options on you fone, and go to gallery or wherever you have saved it to, then click on the file to play the audio,
you must have quick fingers as you will spoil the prank as they will be waiting!
p.s remember to withold you number
if you want to preview them on your computer first try downloading a convertor like this one.
http://www.miksoft.net/mobileAMRconverter.htm