how do i trace phone numbers from voip itouch apps?

i got a few phone calls earlier and i did not recognize the number, this kid sounded 12 or 13 maybe 14, i told my friend to call it back but he said it was 1 of those itouch apps that lets u call people, but then i tried calling back and the kid answered i just could not hear him very well, so if any 1 could figure out how to trace the itouch voip apps or just regular phone numbers please tell
also he called me by my Youtube.com name and said r u ____________(my youtube name) and then said maan ur a fag and then went babbleing on i do make videos and all of that but ive never ever given out my number anywhere so im confused