Bonjour
there's a few thread here and there about that.
http://www.picbasic.co.uk/forum/showthread.php?t=219
http://www.picbasic.co.uk/forum/showthread.php?t=5190

You're on the right forum section. Just spend few hours to read them. Pretty sure you'll find few info.

here's something you should look too
http://pinouts.ru/pin_CellularPhonesCables.shtml

bonne chance!