well i edited this old tone years ago adding the extra beeps for the intro to the SMS , used it on many phones in the past and now converted it for the iPhone
the thread title says it all
i used BlazeMedia Pro to edit it and MP3Gain to make it louder then converted it
just SSH it to your iphone -- /System/Library/Audio/UISounds
sms-received4.caf can renamed to replace the original SMS of your choice
(replace then reboot your iPhone )